From 260263b4722d02ca07bbbb56d2beab95b45d9118 Mon Sep 17 00:00:00 2001
From: zuckerberg <5-zuckerberg@users.noreply.git.neet.dev>
Date: Wed, 7 Dec 2022 22:54:13 -0700
Subject: [PATCH] Day 7

---
 days/7/input        | 986 ++++++++++++++++++++++++++++++++++++++++++++
 days/7/puzzle.txt   | 102 +++++
 days/7/solution.nix |  60 +++
 util.nix            |  10 +
 4 files changed, 1158 insertions(+)
 create mode 100644 days/7/input
 create mode 100644 days/7/puzzle.txt
 create mode 100644 days/7/solution.nix

diff --git a/days/7/input b/days/7/input
new file mode 100644
index 0000000..f39fa1c
--- /dev/null
+++ b/days/7/input
@@ -0,0 +1,986 @@
+$ cd /
+$ ls
+dir bnl
+dir dmpsnhdh
+272080 dncdssn.hdr
+dir fcnqg
+6067 hjpmqrq
+dir jvwtm
+dir ldztz
+dir lmmw
+dir wthvqw
+dir zpdnprb
+$ cd bnl
+$ ls
+dir dhw
+dir dmpsnhdh
+dir lmw
+dir vgbqbrst
+$ cd dhw
+$ ls
+237421 vccwmhl
+$ cd ..
+$ cd dmpsnhdh
+$ ls
+dir chf
+dir mjpbhjm
+dir zwhpwp
+$ cd chf
+$ ls
+4679 lmw.wmp
+217367 wwnfv.qqr
+dir zfgznbz
+$ cd zfgznbz
+$ ls
+179409 cnj.gdn
+171574 vglqg
+$ cd ..
+$ cd ..
+$ cd mjpbhjm
+$ ls
+dir crf
+dir hqnj
+dir lmw
+18783 lmw.rwr
+302608 twpq
+166891 vqczlg
+$ cd crf
+$ ls
+32183 dltmqht
+240428 frqqdsr.hbf
+224910 sgtnrvrt
+$ cd ..
+$ cd hqnj
+$ ls
+261723 cgstb
+77979 dmpsnhdh.cmd
+$ cd ..
+$ cd lmw
+$ ls
+50307 fcqrwd
+$ cd ..
+$ cd ..
+$ cd zwhpwp
+$ ls
+141133 gdngm.mps
+$ cd ..
+$ cd ..
+$ cd lmw
+$ ls
+dir dvv
+267473 jmqgrh.dlz
+295139 rrqjwpm
+$ cd dvv
+$ ls
+114536 gmlmbrrw.wdm
+102061 lmw
+$ cd ..
+$ cd ..
+$ cd vgbqbrst
+$ ls
+105102 dmpsnhdh.bgl
+269054 gmwgjf.fzz
+dir jbdtpnw
+245266 jzsjvgl
+216220 lmw.gtb
+dir rflp
+dir twpq
+$ cd jbdtpnw
+$ ls
+27543 cjvvmzp
+$ cd ..
+$ cd rflp
+$ ls
+137601 frqqdsr.hbf
+83444 rrqjwpm
+$ cd ..
+$ cd twpq
+$ ls
+dir rlbsdj
+36846 tnrqzjdd
+$ cd rlbsdj
+$ ls
+56078 bvndq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dmpsnhdh
+$ ls
+dir fnpwwhtj
+dir lmw
+9090 mgjpsvl.jlh
+186374 pbb.zln
+$ cd fnpwwhtj
+$ ls
+dir cgp
+$ cd cgp
+$ ls
+81938 hjpmqrq
+281971 jvszf
+151057 wmr.bnf
+$ cd ..
+$ cd ..
+$ cd lmw
+$ ls
+dir bfbv
+56929 pbb.zln
+dir rrqjwpm
+dir sngm
+$ cd bfbv
+$ ls
+92667 qrrttb.jgp
+$ cd ..
+$ cd rrqjwpm
+$ ls
+25739 cqljn.zqw
+91325 dncdssn.hdr
+$ cd ..
+$ cd sngm
+$ ls
+282163 jgrj
+dir lmw
+237524 lmw.dff
+153497 lmw.ntg
+dir lqd
+dir szn
+143535 tvpvc.qpr
+98326 vbfgh
+$ cd lmw
+$ ls
+32484 dncdssn.hdr
+dir glwr
+$ cd glwr
+$ ls
+144719 frqqdsr.hbf
+$ cd ..
+$ cd ..
+$ cd lqd
+$ ls
+231401 dncdssn.hdr
+dir jnjqmvg
+dir lmw
+199704 rrqjwpm
+$ cd jnjqmvg
+$ ls
+104947 trpsrfjz.brg
+$ cd ..
+$ cd lmw
+$ ls
+230298 rrqjwpm.nnv
+158947 wfv.qrb
+$ cd ..
+$ cd ..
+$ cd szn
+$ ls
+197974 frqqdsr.hbf
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd fcnqg
+$ ls
+251609 dncdssn.hdr
+289497 jdjmftqs
+228459 qbmthcq
+$ cd ..
+$ cd jvwtm
+$ ls
+dir dmpsnhdh
+47959 pbb.zln
+dir tlr
+dir twpq
+dir wbgcsw
+dir zjmldjdh
+$ cd dmpsnhdh
+$ ls
+247567 bnl
+102471 bnl.wdm
+80054 fhqvp.hfm
+dir llhp
+dir mnsbh
+dir mpplsfjp
+20844 mtvl.lmp
+$ cd llhp
+$ ls
+180255 dmpsnhdh
+$ cd ..
+$ cd mnsbh
+$ ls
+267627 dmpsnhdh
+$ cd ..
+$ cd mpplsfjp
+$ ls
+dir bnl
+233742 tcnpvqc.tdr
+$ cd bnl
+$ ls
+243223 fcqrwd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd tlr
+$ ls
+dir vcsngm
+dir wndmt
+$ cd vcsngm
+$ ls
+36434 czs.dnv
+$ cd ..
+$ cd wndmt
+$ ls
+dir fvmtfcqd
+dir nvdb
+dir nwqqgl
+dir sbspgnpm
+$ cd fvmtfcqd
+$ ls
+237025 nzttjt.rzh
+$ cd ..
+$ cd nvdb
+$ ls
+235328 dnrqwqtp.vfc
+51984 rhblt.mfz
+51332 rjhvhw
+$ cd ..
+$ cd nwqqgl
+$ ls
+203534 cjghw
+dir cljbrh
+$ cd cljbrh
+$ ls
+133820 lmw.dnd
+$ cd ..
+$ cd ..
+$ cd sbspgnpm
+$ ls
+270010 hjpmqrq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd twpq
+$ ls
+dir dmpsnhdh
+dir hbchdjjp
+247649 hjpmqrq
+29891 rrqjwpm
+72407 twpq.crb
+$ cd dmpsnhdh
+$ ls
+251490 dncdssn.hdr
+222231 hjpmqrq
+102058 pbb.zln
+$ cd ..
+$ cd hbchdjjp
+$ ls
+70058 dprrmd.qcd
+230958 tsdbl.bnq
+$ cd ..
+$ cd ..
+$ cd wbgcsw
+$ ls
+292028 bhtfcf
+dir bnl
+dir bqq
+dir ctnlpgt
+247888 hblhfvwj
+dir hbqm
+277949 pbb.zln
+106225 rrqjwpm
+125927 ssqpmlfb.gwm
+dir zqmjwsgz
+dir zwwphs
+$ cd bnl
+$ ls
+dir fbbr
+240500 frqqdsr.hbf
+dir mzfrdl
+25137 srqlww.mcj
+dir tqgrdz
+dir ztrnq
+$ cd fbbr
+$ ls
+84414 mjbw.dhs
+$ cd ..
+$ cd mzfrdl
+$ ls
+135647 bccwgn
+dir cjdptqgh
+dir hwdnrqns
+dir prq
+$ cd cjdptqgh
+$ ls
+147946 mdgl.drz
+11972 pbb.zln
+$ cd ..
+$ cd hwdnrqns
+$ ls
+dir dmpsnhdh
+$ cd dmpsnhdh
+$ ls
+254432 phthmn
+$ cd ..
+$ cd ..
+$ cd prq
+$ ls
+75827 dmpsnhdh.rtl
+$ cd ..
+$ cd ..
+$ cd tqgrdz
+$ ls
+251475 bjwnll.rlw
+$ cd ..
+$ cd ztrnq
+$ ls
+208497 bnl.dtr
+179376 gqnbswcj.hht
+$ cd ..
+$ cd ..
+$ cd bqq
+$ ls
+202201 bnl.lbm
+$ cd ..
+$ cd ctnlpgt
+$ ls
+269484 vsfvzrpr
+$ cd ..
+$ cd hbqm
+$ ls
+74455 bvnfz
+42748 pbb.zln
+$ cd ..
+$ cd zqmjwsgz
+$ ls
+146194 pbb.zln
+$ cd ..
+$ cd zwwphs
+$ ls
+209587 mtbzd.nwb
+$ cd ..
+$ cd ..
+$ cd zjmldjdh
+$ ls
+dir cdq
+dir mdclfbs
+dir tfc
+132043 wrm
+$ cd cdq
+$ ls
+289173 twpq.mrn
+$ cd ..
+$ cd mdclfbs
+$ ls
+64639 bnl.jwf
+dir hpdgt
+72868 hznfj.nmj
+159467 lmw.bfz
+$ cd hpdgt
+$ ls
+52760 fcqrwd
+54661 tzgt.hvh
+$ cd ..
+$ cd ..
+$ cd tfc
+$ ls
+185481 bwntlh
+18925 fcqrwd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ldztz
+$ ls
+128430 bwz.fcz
+dir dmpsnhdh
+dir lbqgz
+dir znrnj
+$ cd dmpsnhdh
+$ ls
+238193 dncdssn.hdr
+285939 hwfngq.dpw
+$ cd ..
+$ cd lbqgz
+$ ls
+171931 vgrp
+$ cd ..
+$ cd znrnj
+$ ls
+153738 vmwwbjqd
+$ cd ..
+$ cd ..
+$ cd lmmw
+$ ls
+dir bqqnsfdj
+163303 fcqrwd
+43453 frqqdsr.hbf
+33319 hjpmqrq
+dir rlpcqtzg
+$ cd bqqnsfdj
+$ ls
+dir bnl
+2251 hjpmqrq
+14707 rrqjwpm
+dir tlnbvhdl
+$ cd bnl
+$ ls
+33357 bnl.fqp
+151237 bnl.vbs
+40294 dmpsnhdh.hwz
+76455 dncdssn.hdr
+290341 hjpmqrq
+dir lmw
+dir nqw
+$ cd lmw
+$ ls
+dir sfj
+$ cd sfj
+$ ls
+156532 fcqrwd
+$ cd ..
+$ cd ..
+$ cd nqw
+$ ls
+59928 dncdssn.hdr
+$ cd ..
+$ cd ..
+$ cd tlnbvhdl
+$ ls
+183301 hjpmqrq
+$ cd ..
+$ cd ..
+$ cd rlpcqtzg
+$ ls
+258638 dqt.mlc
+$ cd ..
+$ cd ..
+$ cd wthvqw
+$ ls
+224501 pbb.zln
+$ cd ..
+$ cd zpdnprb
+$ ls
+dir bnl
+dir ffg
+dir jljlwpsv
+212081 lrzc.lhj
+dir rrqjwpm
+dir twpq
+dir vlgsrtm
+$ cd bnl
+$ ls
+124009 hjgjf
+74860 hjpmqrq
+84996 lrdl.swf
+dir pnzmp
+$ cd pnzmp
+$ ls
+dir btbtlrs
+128636 nfzf
+$ cd btbtlrs
+$ ls
+107651 hhzbwd.wzj
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ffg
+$ ls
+57918 jwzbs.tnt
+$ cd ..
+$ cd jljlwpsv
+$ ls
+188175 dmpsnhdh.nnb
+46693 fcqrwd
+111557 pbb.zln
+$ cd ..
+$ cd rrqjwpm
+$ ls
+dir bftw
+dir ccsfws
+87225 mccw
+290654 pbb.zln
+147394 twzqc.pbz
+52983 wsvgf
+dir wwfgbzqh
+$ cd bftw
+$ ls
+dir brl
+167154 crs
+dir lmw
+dir rrqjwpm
+dir twpq
+174963 twpq.wjl
+dir vnfhb
+dir wcldzp
+$ cd brl
+$ ls
+297937 wspcnp
+$ cd ..
+$ cd lmw
+$ ls
+166695 mcjql.jrv
+$ cd ..
+$ cd rrqjwpm
+$ ls
+198762 mwn
+$ cd ..
+$ cd twpq
+$ ls
+141835 jlwf.hcd
+$ cd ..
+$ cd vnfhb
+$ ls
+128626 tvmwhq.wfn
+$ cd ..
+$ cd wcldzp
+$ ls
+dir ncq
+dir twpq
+$ cd ncq
+$ ls
+dir wrtw
+$ cd wrtw
+$ ls
+133331 fcqrwd
+$ cd ..
+$ cd ..
+$ cd twpq
+$ ls
+151811 fcqrwd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ccsfws
+$ ls
+100548 twpq.ppm
+$ cd ..
+$ cd wwfgbzqh
+$ ls
+dir lmw
+dir mfms
+dir pjbjgbcl
+204154 qtflzwm
+226500 vdmjj.htj
+dir wzqbwr
+$ cd lmw
+$ ls
+dir bgl
+95150 dncdssn.hdr
+119653 frqqdsr.hbf
+97941 hjpmqrq
+dir jqthwzj
+$ cd bgl
+$ ls
+dir lmw
+dir rrqjwpm
+$ cd lmw
+$ ls
+233655 wmdldvbz
+$ cd ..
+$ cd rrqjwpm
+$ ls
+242918 frqqdsr.hbf
+227581 hjpmqrq
+dir hsvnmlp
+dir nsch
+25524 pbb.zln
+dir qlgg
+dir twpq
+67453 twpq.fms
+$ cd hsvnmlp
+$ ls
+264517 pbb.zln
+$ cd ..
+$ cd nsch
+$ ls
+7898 cmsdzh
+233270 dmpsnhdh.bsq
+101256 frl
+133902 jzvh.vdv
+dir lmw
+dir sgjsg
+130245 wcftvft
+$ cd lmw
+$ ls
+69572 bnjnc.csp
+$ cd ..
+$ cd sgjsg
+$ ls
+38856 tnzpz.tbq
+$ cd ..
+$ cd ..
+$ cd qlgg
+$ ls
+276013 frbstg.pzb
+$ cd ..
+$ cd twpq
+$ ls
+136454 fhwz.bqb
+94099 rglp
+114026 tsrt.cbd
+26252 zhclpzm.rqf
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd jqthwzj
+$ ls
+128200 lmw.btl
+$ cd ..
+$ cd ..
+$ cd mfms
+$ ls
+274935 dmpsnhdh
+76547 lchwq.dsd
+215701 pbb.zln
+dir rmwtvjt
+$ cd rmwtvjt
+$ ls
+74490 hjpmqrq
+$ cd ..
+$ cd ..
+$ cd pjbjgbcl
+$ ls
+231757 cjcpwwc.wbf
+dir cswvftzs
+dir jtvtg
+dir lmw
+dir tnctbjr
+dir tqsrfhdr
+$ cd cswvftzs
+$ ls
+dir dchqnbns
+dir smf
+$ cd dchqnbns
+$ ls
+94111 szl.hqs
+$ cd ..
+$ cd smf
+$ ls
+dir dlnsgvl
+dir zglt
+$ cd dlnsgvl
+$ ls
+dir dsz
+$ cd dsz
+$ ls
+156473 hjpmqrq
+$ cd ..
+$ cd ..
+$ cd zglt
+$ ls
+295383 frgg.sdp
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd jtvtg
+$ ls
+202254 bftv.rqb
+58419 lmw
+$ cd ..
+$ cd lmw
+$ ls
+8097 fcqrwd
+$ cd ..
+$ cd tnctbjr
+$ ls
+250830 frqqdsr.hbf
+dir gzrcqr
+$ cd gzrcqr
+$ ls
+dir fnzgsnv
+$ cd fnzgsnv
+$ ls
+117215 hjpmqrq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd tqsrfhdr
+$ ls
+96381 lmw
+$ cd ..
+$ cd ..
+$ cd wzqbwr
+$ ls
+149066 dmpsnhdh.vnd
+dir dpbcgfdr
+dir swp
+14495 twpq.gsb
+dir zhj
+$ cd dpbcgfdr
+$ ls
+12909 dmpsnhdh
+dir jvn
+173491 mnhpr.lpr
+222018 rfqfjmd.jqq
+205077 wbbdrpr.hzj
+dir wzpbbbhm
+$ cd jvn
+$ ls
+117656 vqddrqlq.nfd
+233109 vqqvh.swz
+$ cd ..
+$ cd wzpbbbhm
+$ ls
+143534 pbb.zln
+$ cd ..
+$ cd ..
+$ cd swp
+$ ls
+131295 pbb.zln
+$ cd ..
+$ cd zhj
+$ ls
+166268 pbb.zln
+33734 rrqjwpm.blg
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd twpq
+$ ls
+dir bppvlwqs
+dir bvh
+dir rmcdr
+dir tdn
+2230 whb.lfb
+dir wwtwnvh
+$ cd bppvlwqs
+$ ls
+195026 hvlhgsw
+279259 rrqjwpm
+$ cd ..
+$ cd bvh
+$ ls
+dir lmw
+$ cd lmw
+$ ls
+66958 pdqnd
+$ cd ..
+$ cd ..
+$ cd rmcdr
+$ ls
+dir dmpsnhdh
+182930 grj
+dir pmrdhrth
+119725 qpcqclqh
+77890 sjgfjz
+142855 twpq
+dir zbmcrvbh
+$ cd dmpsnhdh
+$ ls
+dir rrqjwpm
+188474 zgjzpbl.vgv
+$ cd rrqjwpm
+$ ls
+dir bnl
+dir lmw
+7598 vsntvs.pdv
+$ cd bnl
+$ ls
+245600 lmw.mgf
+$ cd ..
+$ cd lmw
+$ ls
+73396 hjpmqrq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pmrdhrth
+$ ls
+173155 rrqjwpm.pjw
+178530 smgpzs.qtj
+$ cd ..
+$ cd zbmcrvbh
+$ ls
+124201 fcqrwd
+135578 hjpmqrq
+54356 hnztplsp.qlh
+dir lmw
+58350 pbb.zln
+dir qfrvdm
+dir rcg
+15267 rwbzjpt.djn
+$ cd lmw
+$ ls
+dir bbbll
+28362 bfgfwlf.wvg
+229637 dmpndms.fln
+146121 dncdssn.hdr
+131039 frqqdsr.hbf
+152805 hjpmqrq
+dir mlz
+$ cd bbbll
+$ ls
+169940 dncdssn.hdr
+216888 pbb.zln
+248369 tjpmlr.vmf
+$ cd ..
+$ cd mlz
+$ ls
+115167 bhfv.fts
+$ cd ..
+$ cd ..
+$ cd qfrvdm
+$ ls
+284564 pbb.zln
+$ cd ..
+$ cd rcg
+$ ls
+dir sqzjz
+$ cd sqzjz
+$ ls
+116435 jrstpcpl.zsq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd tdn
+$ ls
+143971 cmg
+133317 fcqrwd
+dir pstpclp
+133161 tddv
+$ cd pstpclp
+$ ls
+267351 hjpmqrq
+86930 rrqjwpm.dvl
+$ cd ..
+$ cd ..
+$ cd wwtwnvh
+$ ls
+256584 frqqdsr.hbf
+114564 twpq.wrd
+$ cd ..
+$ cd ..
+$ cd vlgsrtm
+$ ls
+148089 bnl.jzj
+119796 cjfphsfw.hnd
+197668 cpw
+dir dmpsnhdh
+dir fjsglr
+dir lmw
+dir lqgrft
+9231 pltdltrs
+dir rmdp
+109777 rncfff.fll
+dir vgjzqjpq
+dir ztnqnfnq
+$ cd dmpsnhdh
+$ ls
+dir lltnrdtv
+dir scthsg
+$ cd lltnrdtv
+$ ls
+179511 pcvmpz
+90913 tbr
+$ cd ..
+$ cd scthsg
+$ ls
+dir rrqjwpm
+$ cd rrqjwpm
+$ ls
+188629 fcqrwd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd fjsglr
+$ ls
+139754 fcqrwd
+dir pnsjwfzc
+$ cd pnsjwfzc
+$ ls
+113848 lmw
+$ cd ..
+$ cd ..
+$ cd lmw
+$ ls
+54999 dmpsnhdh
+dir ffhcf
+251476 frqqdsr.hbf
+dir jpgqspqw
+198972 nhfclq.pbh
+180380 nqmjnvc.fvr
+dir pfsjwmbc
+213768 rcvccgcd
+$ cd ffhcf
+$ ls
+40478 svmwstq.sjj
+$ cd ..
+$ cd jpgqspqw
+$ ls
+22181 hjpmqrq
+$ cd ..
+$ cd pfsjwmbc
+$ ls
+dir bcvchw
+$ cd bcvchw
+$ ls
+225892 bnl.nwc
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd lqgrft
+$ ls
+dir rrqjwpm
+dir twpq
+$ cd rrqjwpm
+$ ls
+54786 fcqrwd
+3053 tthhqjm.ntd
+$ cd ..
+$ cd twpq
+$ ls
+109355 bnl
+dir lmw
+dir mhgqt
+301291 rrqjwpm.lrm
+271233 twpq.srp
+$ cd lmw
+$ ls
+dir lmw
+dir lngbszqm
+$ cd lmw
+$ ls
+139640 pbb.zln
+$ cd ..
+$ cd lngbszqm
+$ ls
+98279 mqvq.gsj
+283599 rvjd.dvt
+$ cd ..
+$ cd ..
+$ cd mhgqt
+$ ls
+208165 fcqrwd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rmdp
+$ ls
+dir bqn
+170956 fcqrwd
+90954 snnttp.gld
+$ cd bqn
+$ ls
+75628 hdrgbrpc
+$ cd ..
+$ cd ..
+$ cd vgjzqjpq
+$ ls
+dir bnl
+dir wpfw
+$ cd bnl
+$ ls
+25911 pbb.zln
+$ cd ..
+$ cd wpfw
+$ ls
+247784 bzll.ltc
+$ cd ..
+$ cd ..
+$ cd ztnqnfnq
+$ ls
+dir dtpzsrfc
+214055 srgzhp.nlr
+$ cd dtpzsrfc
+$ ls
+142652 bhgwj
\ No newline at end of file
diff --git a/days/7/puzzle.txt b/days/7/puzzle.txt
new file mode 100644
index 0000000..5544366
--- /dev/null
+++ b/days/7/puzzle.txt
@@ -0,0 +1,102 @@
+--- Day 7: No Space Left On Device ---
+
+You can hear birds chirping and raindrops hitting leaves as the expedition proceeds. Occasionally, you can even hear much louder sounds in the distance; how big do the animals get out here, anyway?
+
+The device the Elves gave you has problems with more than just its communication system. You try to run a system update:
+
+$ system-update --please --pretty-please-with-sugar-on-top
+Error: No space left on device
+
+Perhaps you can delete some files to make space for the update?
+
+You browse around the filesystem to assess the situation and save the resulting terminal output (your puzzle input). For example:
+
+$ cd /
+$ ls
+dir a
+14848514 b.txt
+8504156 c.dat
+dir d
+$ cd a
+$ ls
+dir e
+29116 f
+2557 g
+62596 h.lst
+$ cd e
+$ ls
+584 i
+$ cd ..
+$ cd ..
+$ cd d
+$ ls
+4060174 j
+8033020 d.log
+5626152 d.ext
+7214296 k
+
+The filesystem consists of a tree of files (plain data) and directories (which can contain other directories or files). The outermost directory is called /. You can navigate around the filesystem, moving into or out of directories and listing the contents of the directory you're currently in.
+
+Within the terminal output, lines that begin with $ are commands you executed, very much like some modern computers:
+
+    cd means change directory. This changes which directory is the current directory, but the specific result depends on the argument:
+        cd x moves in one level: it looks in the current directory for the directory named x and makes it the current directory.
+        cd .. moves out one level: it finds the directory that contains the current directory, then makes that directory the current directory.
+        cd / switches the current directory to the outermost directory, /.
+    ls means list. It prints out all of the files and directories immediately contained by the current directory:
+        123 abc means that the current directory contains a file named abc with size 123.
+        dir xyz means that the current directory contains a directory named xyz.
+
+Given the commands and output in the example above, you can determine that the filesystem looks visually like this:
+
+- / (dir)
+  - a (dir)
+    - e (dir)
+      - i (file, size=584)
+    - f (file, size=29116)
+    - g (file, size=2557)
+    - h.lst (file, size=62596)
+  - b.txt (file, size=14848514)
+  - c.dat (file, size=8504156)
+  - d (dir)
+    - j (file, size=4060174)
+    - d.log (file, size=8033020)
+    - d.ext (file, size=5626152)
+    - k (file, size=7214296)
+
+Here, there are four directories: / (the outermost directory), a and d (which are in /), and e (which is in a). These directories also contain files of various sizes.
+
+Since the disk is full, your first step should probably be to find directories that are good candidates for deletion. To do this, you need to determine the total size of each directory. The total size of a directory is the sum of the sizes of the files it contains, directly or indirectly. (Directories themselves do not count as having any intrinsic size.)
+
+The total sizes of the directories above can be found as follows:
+
+    The total size of directory e is 584 because it contains a single file i of size 584 and no other directories.
+    The directory a has total size 94853 because it contains files f (size 29116), g (size 2557), and h.lst (size 62596), plus file i indirectly (a contains e which contains i).
+    Directory d has total size 24933642.
+    As the outermost directory, / contains every file. Its total size is 48381165, the sum of the size of every file.
+
+To begin, find all of the directories with a total size of at most 100000, then calculate the sum of their total sizes. In the example above, these directories are a and e; the sum of their total sizes is 95437 (94853 + 584). (As in this example, this process can count files more than once!)
+
+Find all of the directories with a total size of at most 100000. What is the sum of the total sizes of those directories?
+
+Your puzzle answer was 1444896.
+--- Part Two ---
+
+Now, you're ready to choose a directory to delete.
+
+The total disk space available to the filesystem is 70000000. To run the update, you need unused space of at least 30000000. You need to find a directory you can delete that will free up enough space to run the update.
+
+In the example above, the total size of the outermost directory (and thus the total amount of used space) is 48381165; this means that the size of the unused space must currently be 21618835, which isn't quite the 30000000 required by the update. Therefore, the update still requires a directory with total size of at least 8381165 to be deleted before it can run.
+
+To achieve this, you have the following options:
+
+    Delete directory e, which would increase unused space by 584.
+    Delete directory a, which would increase unused space by 94853.
+    Delete directory d, which would increase unused space by 24933642.
+    Delete directory /, which would increase unused space by 48381165.
+
+Directories e and a are both too small; deleting them would not free up enough space. However, directories d and / are both big enough! Between these, choose the smallest: d, increasing unused space by 24933642.
+
+Find the smallest directory that, if deleted, would free up enough space on the filesystem to run the update. What is the total size of that directory?
+
+Your puzzle answer was 404395.
\ No newline at end of file
diff --git a/days/7/solution.nix b/days/7/solution.nix
new file mode 100644
index 0000000..ac59bc4
--- /dev/null
+++ b/days/7/solution.nix
@@ -0,0 +1,60 @@
+with import ../../util.nix;
+
+let
+  # read input
+  cmdOuts = splitString "\n$ " (removePrefix "$ " (readFile ./input));
+
+  fileTree =
+    let
+      start = { cwd = []; tree = {}; };
+
+      applyCmd = acc: cmdOut:
+        let
+          # parse cmd + cmd output
+          lines = splitString "\n" cmdOut;
+          cmd = splitString " " (head lines);
+          out = tail lines;
+
+          # apply cmds
+          applyCd = cwd: param:
+            if param == ".." then dropLast cwd
+            else if param == "/" then []
+            else cwd ++ [param];
+          applyLs = cwd: param:
+            let
+              parseFileDir = splitLine:
+                if head splitLine == "dir" then { ${last splitLine} = {}; }
+                else { ${last splitLine} = toInt (head splitLine); };
+              makeSubTree = combineAttrs (map (line: parseFileDir (splitString " " line)) param);
+            in
+              setAttrByPath cwd makeSubTree;
+        in 
+          if head cmd == "cd" then
+            { inherit (acc) tree; cwd = applyCd acc.cwd (last cmd);  }
+          else # ls
+            { inherit (acc) cwd; tree = recursiveUpdate acc.tree (applyLs acc.cwd out); };
+    in (foldl applyCmd start cmdOuts).tree;
+
+  sizeOfDir = dir:
+    sum (map (v: if isAttrs v then sizeOfDir v else v) (attrValues dir));
+
+  # a flat list of sizes for all directories
+  dirSizes = recurisveVisitAttrs (n: v: if isAttrs v then sizeOfDir v else 0) fileTree;
+
+  # a list of sizes for small directories
+  smallDirSizes =
+    foldl (acc: size: if size < 100000 && size != 0 then acc ++ [size] else acc) [] dirSizes;
+
+  totalUsedSize = sizeOfDir fileTree;
+
+  # smallest directory to delete to free target size
+  minDirOfAtLeastSize = targetSize: foldl (acc: s: if s >= targetSize && s < acc then s else acc) totalUsedSize dirSizes;
+
+  totalFsSize = 70000000;
+  fsSizeNeeded = 30000000;
+  availableSpace = totalFsSize - totalUsedSize;
+  spaceNeeded = fsSizeNeeded - availableSpace;
+in rec {
+  part1 = sum smallDirSizes;
+  part2 = minDirOfAtLeastSize spaceNeeded;
+}
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diff --git a/util.nix b/util.nix
index 831b26c..84da666 100644
--- a/util.nix
+++ b/util.nix
@@ -31,6 +31,16 @@ let
         outerSize = length ll;
         innerSize = length (elemAt ll 0);
       in genList (i: genList (j: elemAt (elemAt ll j) i) outerSize) innerSize;
+    # attriset recursiveUpdate but for a list of attrisets
+    combineAttrs = foldl recursiveUpdate {};
+    # visits every single attriset element of an attriset recursively
+    # and accumulates the result of every visit in a flat list
+    recurisveVisitAttrs = f: set:
+      let
+        visitor = n: v:
+          if isAttrs v then [(f n v)] ++ recurisveVisitAttrs f v
+          else [(f n v)];
+      in concatLists (map (name: visitor name set.${name}) (attrNames set));
   };
 in
 lib // lib.strings // builtins // utils
\ No newline at end of file