diff --git a/day7/Cargo.lock b/day7/Cargo.lock
new file mode 100644
index 0000000..7af9b93
--- /dev/null
+++ b/day7/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day7"
+version = "0.1.0"
diff --git a/day7/Cargo.toml b/day7/Cargo.toml
new file mode 100644
index 0000000..b170ccb
--- /dev/null
+++ b/day7/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day7"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/day7/input.txt b/day7/input.txt
new file mode 100644
index 0000000..b9cccb9
--- /dev/null
+++ b/day7/input.txt
@@ -0,0 +1,1101 @@
+$ cd /
+$ ls
+dir grdd
+270251 hjlvwtph.jzv
+230026 jzmgcj.gmd
+dir nns
+dir rrfflbql
+$ cd grdd
+$ ls
+233044 mqbz.fcp
+dir nnch
+82939 rgtvsqsh.psq
+150253 srvg.dth
+$ cd nnch
+$ ls
+4014 mqbz.fcp
+$ cd ..
+$ cd ..
+$ cd nns
+$ ls
+dir cgbdghtd
+dir dnh
+dir gjhp
+dir jwjm
+dir mrpfzd
+dir ncvv
+dir pfnglqgw
+dir tlh
+dir vnrhpc
+$ cd cgbdghtd
+$ ls
+276941 jrrcdgz.szm
+$ cd ..
+$ cd dnh
+$ ls
+269539 nnch
+220637 sjzmpwwb
+$ cd ..
+$ cd gjhp
+$ ls
+dir czclvmwc
+dir jgtzfsm
+$ cd czclvmwc
+$ ls
+179729 fzqvvlg
+67916 pmsdthr.prv
+$ cd ..
+$ cd jgtzfsm
+$ ls
+151591 rcggj.nwm
+$ cd ..
+$ cd ..
+$ cd jwjm
+$ ls
+203559 nnch
+$ cd ..
+$ cd mrpfzd
+$ ls
+dir pfnglqgw
+204978 qscs.vpq
+16184 tbfwpmp.hvl
+$ cd pfnglqgw
+$ ls
+dir wvzw
+dir ztl
+$ cd wvzw
+$ ls
+195912 jpn.ndh
+143238 nnch.djz
+2239 pmsdthr.prv
+dir sfqq
+$ cd sfqq
+$ ls
+134913 pthmqd
+dir vcdhz
+$ cd vcdhz
+$ ls
+13800 ffhv.jnq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ztl
+$ ls
+181007 mqbz.fcp
+266517 zbpjz.gbr
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ncvv
+$ ls
+296494 ccmvjm.bjb
+20801 hjr
+32494 mqbz.fcp
+dir nnch
+dir pfnglqgw
+dir qpq
+dir rftzzmq
+dir wgblcl
+294511 wrdmgdb.fmh
+$ cd nnch
+$ ls
+dir hjzpfvm
+dir ncvv
+dir pffr
+dir pfnglqgw
+dir ssdffgsq
+$ cd hjzpfvm
+$ ls
+304078 mqbz.fcp
+dir nnch
+146425 nnch.lrw
+dir vcfglm
+dir zhscvh
+$ cd nnch
+$ ls
+311625 gqmpvplj.vjg
+248744 ndfcj
+$ cd ..
+$ cd vcfglm
+$ ls
+dir btptvs
+dir ghpvzvzp
+146354 nnch
+$ cd btptvs
+$ ls
+127157 nqnnwq.rtz
+16115 pmsdthr.prv
+$ cd ..
+$ cd ghpvzvzp
+$ ls
+dir ncvv
+$ cd ncvv
+$ ls
+236869 pmsdthr.prv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zhscvh
+$ ls
+225337 glpz
+$ cd ..
+$ cd ..
+$ cd ncvv
+$ ls
+dir nljtcssr
+dir svjhsvjh
+$ cd nljtcssr
+$ ls
+258085 gqmpvplj.vjg
+dir ncvv
+dir qmzfgcr
+249049 wznr.gbs
+dir zvvpqlmq
+$ cd ncvv
+$ ls
+147686 ndfcj.sfr
+$ cd ..
+$ cd qmzfgcr
+$ ls
+162245 ndfcj.nlj
+$ cd ..
+$ cd zvvpqlmq
+$ ls
+160481 ggnc
+$ cd ..
+$ cd ..
+$ cd svjhsvjh
+$ ls
+dir bjqbmt
+58138 gqmpvplj.vjg
+dir nsvf
+154398 rrhjs.gch
+dir wmvhmlr
+$ cd bjqbmt
+$ ls
+252614 ndfcj.wzg
+153886 nnch
+214625 zhmdvb
+$ cd ..
+$ cd nsvf
+$ ls
+274932 nnch.jfg
+$ cd ..
+$ cd wmvhmlr
+$ ls
+137205 nnch
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pffr
+$ ls
+89895 cwpnzngf.swg
+197833 jgv
+184768 jjhzddp.fbb
+31033 tpngfdsg.brv
+$ cd ..
+$ cd pfnglqgw
+$ ls
+228015 ccmvjm.bjb
+$ cd ..
+$ cd ssdffgsq
+$ ls
+165887 gqmpvplj.vjg
+dir lfq
+dir nnch
+170828 qjb.mnp
+dir ttj
+$ cd lfq
+$ ls
+257411 gqmpvplj.vjg
+137375 jzmgcj.gmd
+267329 nsbsgd.zvq
+$ cd ..
+$ cd nnch
+$ ls
+dir mrfwfq
+171186 ndhqthf.jlp
+$ cd mrfwfq
+$ ls
+100447 lsfsh.mvr
+$ cd ..
+$ cd ..
+$ cd ttj
+$ ls
+49634 ndfcj
+dir tqvld
+$ cd tqvld
+$ ls
+dir ndfcj
+$ cd ndfcj
+$ ls
+dir gnzj
+80690 pmlnbvj
+12843 zbrfmfgj.lzr
+$ cd gnzj
+$ ls
+dir wtpzrpn
+$ cd wtpzrpn
+$ ls
+33840 gqmpvplj.vjg
+18122 rrfflbql.vws
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pfnglqgw
+$ ls
+289092 fdjfvb
+$ cd ..
+$ cd qpq
+$ ls
+126281 ccmvjm.bjb
+dir crtzrd
+231988 jzmgcj.gmd
+203061 mgmmp
+272098 mqbz.fcp
+dir pfnglqgw
+dir qzvcsn
+105003 rrfflbql.mcm
+$ cd crtzrd
+$ ls
+162336 fsps
+100215 mctd.wsz
+67983 mqbz.fcp
+281538 mqq.cgz
+dir ndfcj
+dir rrfflbql
+dir wbmtvr
+$ cd ndfcj
+$ ls
+290647 pfjczr.wjc
+$ cd ..
+$ cd rrfflbql
+$ ls
+dir mpr
+dir ncvv
+dir rrfflbql
+301818 zml.qfj
+$ cd mpr
+$ ls
+237300 gqmpvplj.vjg
+dir pfnglqgw
+$ cd pfnglqgw
+$ ls
+dir brnwdjtg
+dir dvqlmzw
+248787 pmsdthr.prv
+$ cd brnwdjtg
+$ ls
+256129 ncvv
+dir ptztp
+$ cd ptztp
+$ ls
+104775 nnch.wlc
+$ cd ..
+$ cd ..
+$ cd dvqlmzw
+$ ls
+25407 twgqbrtl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ncvv
+$ ls
+dir jvwvsm
+62293 jzmgcj.gmd
+261836 mqbz.fcp
+dir vvvrf
+$ cd jvwvsm
+$ ls
+222978 ccmvjm.bjb
+207799 jzmgcj.gmd
+dir pcvsvcn
+248569 pmsdthr.prv
+dir wmd
+$ cd pcvsvcn
+$ ls
+39803 pmsdthr.prv
+$ cd ..
+$ cd wmd
+$ ls
+9516 rfstbvj.nhz
+$ cd ..
+$ cd ..
+$ cd vvvrf
+$ ls
+dir ncvv
+dir znwc
+$ cd ncvv
+$ ls
+110667 jzmgcj.gmd
+$ cd ..
+$ cd znwc
+$ ls
+182248 ndfcj.crv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rrfflbql
+$ ls
+231013 ccmvjm.bjb
+dir jlc
+dir rrfflbql
+79210 ttm.zmw
+$ cd jlc
+$ ls
+28096 ccmvjm.bjb
+113156 pmsdthr.prv
+$ cd ..
+$ cd rrfflbql
+$ ls
+234558 lbg.bpn
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd wbmtvr
+$ ls
+285832 fqhs
+$ cd ..
+$ cd ..
+$ cd pfnglqgw
+$ ls
+110965 nnch
+195414 pmsdthr.prv
+243812 thcpw.jfw
+$ cd ..
+$ cd qzvcsn
+$ ls
+279179 gqmpvplj.vjg
+191705 mhmlfc.czv
+146298 pfnglqgw.ppm
+2775 pmsdthr.prv
+$ cd ..
+$ cd ..
+$ cd rftzzmq
+$ ls
+310418 bddhlvs.rwm
+152681 cdznrjl
+278447 rrfflbql
+dir tmcltf
+$ cd tmcltf
+$ ls
+dir mzr
+$ cd mzr
+$ ls
+24154 ccmvjm.bjb
+dir nnch
+dir rqsbw
+$ cd nnch
+$ ls
+100523 mqbz.fcp
+$ cd ..
+$ cd rqsbw
+$ ls
+64033 czzqg.pcz
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd wgblcl
+$ ls
+235768 dvdzbgv.vwl
+186757 jzmgcj.gmd
+$ cd ..
+$ cd ..
+$ cd pfnglqgw
+$ ls
+129407 zfphqcsf.cfn
+$ cd ..
+$ cd tlh
+$ ls
+89310 jzmgcj.gmd
+21486 nwnbbmr.lsq
+40023 rdmtp.zsf
+$ cd ..
+$ cd vnrhpc
+$ ls
+104731 gqmpvplj.vjg
+176015 grn
+3646 jzmgcj.gmd
+dir ncvv
+45414 nfrj.lvq
+233767 pfnglqgw.bvf
+$ cd ncvv
+$ ls
+252691 ccmvjm.bjb
+dir ncvv
+dir vwv
+dir wwmwfbf
+$ cd ncvv
+$ ls
+306441 qfhhnmqz.snc
+$ cd ..
+$ cd vwv
+$ ls
+56033 rrfflbql
+$ cd ..
+$ cd wwmwfbf
+$ ls
+45964 gqmpvplj.vjg
+118391 mvwl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rrfflbql
+$ ls
+175540 bcw.sqp
+154750 ggncvs.nvn
+dir jqzm
+dir mgbglnr
+192820 ndfcj
+dir pfnglqgw
+217147 qjng.svz
+dir rrfflbql
+$ cd jqzm
+$ ls
+dir ncvv
+dir nfcvcddz
+242934 rjwlgm
+dir wzj
+$ cd ncvv
+$ ls
+298067 pfnglqgw.jdv
+$ cd ..
+$ cd nfcvcddz
+$ ls
+261264 gqmpvplj.vjg
+19464 mqbz.fcp
+121507 ncqhrf
+dir ndfcj
+58485 ndfcj.vhh
+dir rcrzjm
+228359 wnftnshq
+$ cd ndfcj
+$ ls
+309008 bwn
+$ cd ..
+$ cd rcrzjm
+$ ls
+48178 fgzpwhvt
+129342 qns.lnj
+$ cd ..
+$ cd ..
+$ cd wzj
+$ ls
+91384 gqmpvplj.vjg
+dir nnch
+dir rzm
+$ cd nnch
+$ ls
+dir sgbwrl
+$ cd sgbwrl
+$ ls
+dir ndfcj
+$ cd ndfcj
+$ ls
+295624 cbmdr
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rzm
+$ ls
+dir cprj
+86746 dfwsj.hqq
+dir dljnvq
+dir ndfcj
+159465 nsglq
+202670 pfnglqgw.wbh
+29700 rrfflbql.wln
+dir vgtftq
+$ cd cprj
+$ ls
+148192 gqmpvplj.vjg
+165473 hwp.ltc
+$ cd ..
+$ cd dljnvq
+$ ls
+91675 pmsdthr.prv
+$ cd ..
+$ cd ndfcj
+$ ls
+83124 rrfflbql.ghs
+$ cd ..
+$ cd vgtftq
+$ ls
+186744 mqbz.fcp
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd mgbglnr
+$ ls
+dir ddtcz
+dir ncvv
+dir nhpwf
+dir rrfflbql
+203683 ttbc
+dir tvbjgv
+dir wvzcq
+$ cd ddtcz
+$ ls
+61553 wfzj
+$ cd ..
+$ cd ncvv
+$ ls
+37589 ccmvjm.bjb
+87987 dnct
+196537 ndfcj.cqg
+40448 pmsdthr.prv
+$ cd ..
+$ cd nhpwf
+$ ls
+243345 gqmpvplj.vjg
+53165 nnch.gfc
+dir pfnglqgw
+dir vdnnf
+$ cd pfnglqgw
+$ ls
+131411 mhvzv.scz
+142119 nnch.gnt
+$ cd ..
+$ cd vdnnf
+$ ls
+83904 ccmvjm.bjb
+dir czfqdtd
+dir dgblftbz
+dir jnftbbtm
+dir pfbnl
+dir pfnglqgw
+$ cd czfqdtd
+$ ls
+dir nnch
+$ cd nnch
+$ ls
+255744 ndfcj.ldv
+$ cd ..
+$ cd ..
+$ cd dgblftbz
+$ ls
+278883 ncvv.zph
+dir pfnglqgw
+133315 phns.cmq
+130316 sftj
+$ cd pfnglqgw
+$ ls
+174155 vnwtv
+$ cd ..
+$ cd ..
+$ cd jnftbbtm
+$ ls
+255828 nmln
+30605 pfnglqgw
+$ cd ..
+$ cd pfbnl
+$ ls
+8603 ndfcj
+$ cd ..
+$ cd pfnglqgw
+$ ls
+235364 pmsdthr.prv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rrfflbql
+$ ls
+dir gfgbj
+$ cd gfgbj
+$ ls
+215226 jzmgcj.gmd
+$ cd ..
+$ cd ..
+$ cd tvbjgv
+$ ls
+dir nnch
+$ cd nnch
+$ ls
+dir gmsb
+$ cd gmsb
+$ ls
+dir tlqdvpr
+$ cd tlqdvpr
+$ ls
+130013 hzrq.zrg
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd wvzcq
+$ ls
+dir ncvv
+$ cd ncvv
+$ ls
+103168 ccmvjm.bjb
+18537 ncvv
+dir nnch
+dir rrfflbql
+$ cd nnch
+$ ls
+20928 ndfcj.lln
+$ cd ..
+$ cd rrfflbql
+$ ls
+dir lgfwf
+$ cd lgfwf
+$ ls
+dir fmzqt
+dir rrfflbql
+$ cd fmzqt
+$ ls
+301419 gqmpvplj.vjg
+$ cd ..
+$ cd rrfflbql
+$ ls
+dir nbvqch
+$ cd nbvqch
+$ ls
+298966 csqvdql.cwr
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pfnglqgw
+$ ls
+dir bhmndjpq
+203077 fssbcjcm.hvt
+dir lfslp
+dir ncvv
+dir nftdcrl
+dir nnch
+dir pfnglqgw
+dir qfbbnr
+dir wttc
+$ cd bhmndjpq
+$ ls
+299744 cmgwwccb.tvv
+173562 fpwv
+dir hmnbfdtr
+dir jqpcs
+73425 mqbz.fcp
+dir ncvv
+dir ndfcj
+95707 pmsdthr.prv
+dir ptzdv
+dir qzhrsnqh
+dir sbqg
+$ cd hmnbfdtr
+$ ls
+dir pfnglqgw
+dir qmpplbtv
+77228 tvpdstcn.zbb
+$ cd pfnglqgw
+$ ls
+dir dwr
+dir jmgp
+102634 mqbz.fcp
+148654 ncvv
+257637 ncvv.nzn
+286938 rrfflbql
+$ cd dwr
+$ ls
+141669 ndfcj
+9012 ptrlq.stq
+$ cd ..
+$ cd jmgp
+$ ls
+78473 pfnglqgw
+$ cd ..
+$ cd ..
+$ cd qmpplbtv
+$ ls
+202948 wjp.rgt
+$ cd ..
+$ cd ..
+$ cd jqpcs
+$ ls
+290654 fmmcph
+8123 zrr.vqm
+$ cd ..
+$ cd ncvv
+$ ls
+dir hbrttp
+$ cd hbrttp
+$ ls
+128004 nffzj
+$ cd ..
+$ cd ..
+$ cd ndfcj
+$ ls
+dir vscwfsl
+$ cd vscwfsl
+$ ls
+251706 snww.dzb
+$ cd ..
+$ cd ..
+$ cd ptzdv
+$ ls
+113702 nnch
+$ cd ..
+$ cd qzhrsnqh
+$ ls
+118758 gqmpvplj.vjg
+75504 vcnn.stz
+102737 zvv
+$ cd ..
+$ cd sbqg
+$ ls
+287663 bhcpslm.wwt
+dir bqr
+dir czhfphh
+39170 fqn
+dir gqnts
+267314 hlv.ljc
+8701 jqpdpg.prz
+dir ncvv
+211749 psln.pdq
+$ cd bqr
+$ ls
+dir chjfw
+dir dgccfvtl
+219440 fvfsfz
+262276 jzmgcj.gmd
+dir ndfcj
+294287 pfnglqgw.lwh
+163881 rrfflbql
+278231 vgjm.rrh
+$ cd chjfw
+$ ls
+134800 hvmvqbz.bqj
+$ cd ..
+$ cd dgccfvtl
+$ ls
+155579 lwmqrd.wvp
+$ cd ..
+$ cd ndfcj
+$ ls
+144255 ncvv.hrn
+236730 ndfcj
+dir pfz
+$ cd pfz
+$ ls
+297448 rrfflbql.fdt
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd czhfphh
+$ ls
+dir wmws
+$ cd wmws
+$ ls
+14499 ncvv
+$ cd ..
+$ cd ..
+$ cd gqnts
+$ ls
+165940 ccmvjm.bjb
+dir gjcm
+dir hldzdlrl
+dir jtnpgg
+dir nnch
+287896 pmsdthr.prv
+$ cd gjcm
+$ ls
+125716 gqmpvplj.vjg
+dir mhjm
+197155 msspbg
+176407 trtdggnf
+$ cd mhjm
+$ ls
+18749 jzmgcj.gmd
+252999 nnch
+76392 rrfflbql.mzh
+$ cd ..
+$ cd ..
+$ cd hldzdlrl
+$ ls
+dir gzpcgj
+dir rvvgn
+$ cd gzpcgj
+$ ls
+dir vfz
+$ cd vfz
+$ ls
+183852 pmsdthr.prv
+$ cd ..
+$ cd ..
+$ cd rvvgn
+$ ls
+143443 ndfcj
+$ cd ..
+$ cd ..
+$ cd jtnpgg
+$ ls
+dir dhvd
+dir hlmgslbs
+dir rrfflbql
+dir vmqpcm
+$ cd dhvd
+$ ls
+131598 ltr.rph
+$ cd ..
+$ cd hlmgslbs
+$ ls
+173562 rrfflbql
+$ cd ..
+$ cd rrfflbql
+$ ls
+dir ghvmc
+$ cd ghvmc
+$ ls
+311611 jzmgcj.gmd
+$ cd ..
+$ cd ..
+$ cd vmqpcm
+$ ls
+192032 mqbz.fcp
+$ cd ..
+$ cd ..
+$ cd nnch
+$ ls
+112995 ccmvjm.bjb
+$ cd ..
+$ cd ..
+$ cd ncvv
+$ ls
+106711 dswpw.wgr
+46614 jzmgcj.gmd
+115391 mqbz.fcp
+dir nnch
+61970 pmsdthr.prv
+dir rrfflbql
+$ cd nnch
+$ ls
+50060 gqjtv.gcs
+dir lnmmd
+73078 ncvv
+49129 tfb
+dir vgwpcjrl
+dir wnqlrqlf
+$ cd lnmmd
+$ ls
+71780 gqmpvplj.vjg
+$ cd ..
+$ cd vgwpcjrl
+$ ls
+8269 zcspgw
+$ cd ..
+$ cd wnqlrqlf
+$ ls
+dir wzsvhssb
+$ cd wzsvhssb
+$ ls
+187249 jzmgcj.gmd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rrfflbql
+$ ls
+dir bpzmvds
+24889 hfnbzcn
+dir lqffwfr
+274793 nnch.svh
+dir rhwm
+$ cd bpzmvds
+$ ls
+298048 tfnqwpj
+$ cd ..
+$ cd lqffwfr
+$ ls
+dir mzfpbjtl
+$ cd mzfpbjtl
+$ ls
+217469 jzmgcj.gmd
+$ cd ..
+$ cd ..
+$ cd rhwm
+$ ls
+54198 gqmpvplj.vjg
+dir tlnmwhdt
+$ cd tlnmwhdt
+$ ls
+94380 ndfcj.bvv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd lfslp
+$ ls
+dir cmrwvp
+dir cnh
+311549 jgmf.fbs
+dir jtgrbqvj
+166298 pbwsqpcg.whf
+151437 pfnglqgw.mcj
+dir sqlwn
+$ cd cmrwvp
+$ ls
+217666 pmsdthr.prv
+172469 vzw.rqw
+$ cd ..
+$ cd cnh
+$ ls
+84011 jfb.mpt
+$ cd ..
+$ cd jtgrbqvj
+$ ls
+dir dcfpfq
+dir ghhs
+dir ntbmh
+dir pfnglqgw
+$ cd dcfpfq
+$ ls
+159731 pfnglqgw
+$ cd ..
+$ cd ghhs
+$ ls
+104713 blwnhcn
+$ cd ..
+$ cd ntbmh
+$ ls
+174007 jzmgcj.gmd
+dir pfnglqgw
+60549 rrfflbql.scj
+dir zwcdggd
+$ cd pfnglqgw
+$ ls
+49844 rfdw.pqh
+$ cd ..
+$ cd zwcdggd
+$ ls
+135925 ccmvjm.bjb
+1135 gqmpvplj.vjg
+120968 hmgpcj.nbb
+$ cd ..
+$ cd ..
+$ cd pfnglqgw
+$ ls
+184937 ccmvjm.bjb
+128621 llsjsmg.vtv
+dir lsbf
+42834 ndfcj.fwq
+85391 trrchml.sgp
+$ cd lsbf
+$ ls
+192593 cfdtsfq.sln
+289191 nnch.qzj
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd sqlwn
+$ ls
+77962 ccmvjm.bjb
+114288 ndfcj
+$ cd ..
+$ cd ..
+$ cd ncvv
+$ ls
+dir gsd
+$ cd gsd
+$ ls
+14949 jwcp.lmq
+$ cd ..
+$ cd ..
+$ cd nftdcrl
+$ ls
+185409 jzmgcj.gmd
+$ cd ..
+$ cd nnch
+$ ls
+280827 djftt
+dir ljt
+dir ncvv
+dir ndfcj
+33396 qvhndl.pwn
+136204 qvlc.cbr
+14063 rrfflbql.mrq
+130666 vscjncbm.sls
+$ cd ljt
+$ ls
+166514 cgrgbpvw
+55138 jzmgcj.gmd
+$ cd ..
+$ cd ncvv
+$ ls
+dir fhnw
+56003 gqtcgszl.vnf
+145831 jzmgcj.gmd
+dir mwcbd
+dir rclnhb
+$ cd fhnw
+$ ls
+28050 gqmpvplj.vjg
+$ cd ..
+$ cd mwcbd
+$ ls
+288468 ncvv
+$ cd ..
+$ cd rclnhb
+$ ls
+190004 ndjmjbp
+$ cd ..
+$ cd ..
+$ cd ndfcj
+$ ls
+287125 gqmpvplj.vjg
+dir ndfcj
+247237 nnch
+138902 pfnglqgw
+$ cd ndfcj
+$ ls
+143400 ssvsvffz
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pfnglqgw
+$ ls
+dir cwwb
+dir dtf
+97867 mqbz.fcp
+$ cd cwwb
+$ ls
+dir wtz
+$ cd wtz
+$ ls
+300949 zcq
+$ cd ..
+$ cd ..
+$ cd dtf
+$ ls
+28018 gqmpvplj.vjg
+$ cd ..
+$ cd ..
+$ cd qfbbnr
+$ ls
+dir bqmdfjp
+89207 gjfzv
+176709 pmsdthr.prv
+246390 rrfflbql.vdl
+$ cd bqmdfjp
+$ ls
+137504 cwz.jdg
+9191 ncvv
+$ cd ..
+$ cd ..
+$ cd wttc
+$ ls
+279516 ccmvjm.bjb
+115478 lwnpwdqt.jpj
+$ cd ..
+$ cd ..
+$ cd rrfflbql
+$ ls
+162371 nnch.pnm
diff --git a/day7/src/main.rs b/day7/src/main.rs
new file mode 100644
index 0000000..d851602
--- /dev/null
+++ b/day7/src/main.rs
@@ -0,0 +1,91 @@
+use std::env;
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::collections::HashMap;
+
+fn main() {
+    let file = File::open(&env::args().nth(1).unwrap()).unwrap();
+    let mut lines = io::BufReader::new(file).lines();
+    let mut tree = DirTree::new();
+    let mut cwd = 0;
+
+    loop {
+        let tokens: Vec<_> = if let Some(Ok(l)) = lines.next() {
+           l.split_whitespace().map(String::from).collect()
+        } else { break; };
+
+        if tokens[0] == "$" {
+            if tokens[1] == "cd" {
+                if tokens[2] == ".." {
+                    cwd = tree.inodes[cwd].parent.unwrap();
+                } else if tokens[2] == "/" {
+                    cwd = 0;
+                } else {
+                    let subdir = tree.inodes[cwd].subdirs[&tokens[2]];
+                    cwd = subdir;
+                }
+            } else if tokens[1] == "ls" {
+                continue;
+            }
+        } else if tokens[0] == "dir" {
+            tree.add_subdir_to(cwd, tokens[1].clone());
+        } else {
+            tree.add_file_to(
+                cwd,
+                tokens[1].clone(),
+                tokens[0].parse::<usize>().unwrap());
+        }
+    }
+
+    let sum: usize = (0..tree.inodes.len())
+        .map(|inode| tree.size_of(inode))
+        .filter(|size| *size <= 100000)
+        .sum();
+    println!("{:?}", sum);
+}
+
+#[derive(Debug)]
+struct Dir {
+    pub files: HashMap<String, usize>, // file name and size
+    pub subdirs: HashMap<String, usize>, // dir name and index into arena
+    pub parent: Option<usize>, // index into arena
+}
+
+#[derive(Debug)]
+struct DirTree {
+    inodes: Vec<Dir>,
+}
+
+impl DirTree {
+    fn new() -> Self {
+        let newdir = Dir {
+            files: HashMap::new(),
+            subdirs: HashMap::new(),
+            parent: None,
+        };
+        DirTree { inodes: vec![newdir] }
+    }
+
+    fn add_subdir_to(&mut self, idx: usize, name: String) {
+        let newidx = self.inodes.len();
+        let newdir = Dir {
+            files: HashMap::new(),
+            subdirs: HashMap::new(),
+            parent: Some(idx),
+        };
+        self.inodes.push(newdir);
+        self.inodes[idx].subdirs.insert(name, newidx);
+    }
+
+    fn add_file_to(&mut self, idx: usize, name: String, size: usize) {
+        self.inodes[idx].files.insert(name, size);
+    }
+
+    fn size_of(&self, inode: usize) -> usize {
+        let size_files: usize = self.inodes[inode].files.values().sum();
+        let size_dirs: usize = self.inodes[inode].subdirs.values()
+            .fold(0, |acc, subdir_inode| acc + self.size_of(*subdir_inode));
+        size_files + size_dirs
+    }
+}
+
diff --git a/day7/test.txt b/day7/test.txt
new file mode 100644
index 0000000..09a921e
--- /dev/null
+++ b/day7/test.txt
@@ -0,0 +1,23 @@
+$ 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