問題 52, 87, 88 に別解を追加しました

answer/52.md

@@ -6,3 +6,11 @@ $ awk 'FNR==1{$1="";h=$0}FNR!=1{print FILENAME,$0,h,NF-1}' data_U data_V | awk '
 ```
 別解（田代）$ ls data_* | xargs -I@ bash -c 'unmap num=1 @ | sed "s/^/@ /"' | sed 's/^data_//'
 ```
+
+### 読者別解
+
+ by [ktrarai](https://github.com/ktrarai)
+
+```
+$ awk 'FNR == 1 { f = gensub(/data_/, "", 1, FILENAME); n = split($0, h) } FNR > 1 { for (i = 2; i <= n; i++) print f, $1, h[i], $i }' data_[UV]
+```

answer/87.md

@@ -6,3 +6,11 @@ $ cat oct.txt | awk '{$1="";print}' | xargs -n 1 | sed '1iobase=16;ibase=8;' | b
 ```
 別解（山田）$ cut -c8- oct.txt | fmt -1 | perl -nle 'printf pack("s",oct($_));'
 ```
+
+### 読者別解
+
+ by [ktrarai](https://github.com/ktrarai)
+
+```
+$ sed -E 's/^.{7}//; s/[^ ]+/0&/g' oct.txt | xargs printf '%04x' | sed -E 's/(..)(..)/"\\x\2\\x\1"/g' | xargs printf
+```

answer/88.md

@@ -8,3 +8,11 @@ $ cat image_masked.bmp | xxd -b -c1 | sed -n '139,$p' | sed -n '1~3p' | awk '{pr
 別解1（上田）$ tail -c $((64*64*3)) image_masked.bmp | xxd -c1 -b | awk 'NR%3==1{a+=a+$2%2}!(NR%24){printf("%02x",a);a=0}' | xxd -r -p
 別解2（田代、山田）$ xxd -c 1 -b -s $(xxd -p -u -c 1 -s 10 -l 4 image_masked.bmp | tac | tr -d '\n' | dc -e'16i?p') image_masked.bmp | awk 'NR%3==1{printf substr($2,8,1)}' | dc -e'2i?P'
 ```
+
+### 読者別解
+
+ by [ktrarai](https://github.com/ktrarai)
+
+```
+$ cat image_masked.bmp | od -A n -j 10 -N 4 -t u4 | xargs -I @ od -A n -j @ -t u1 -v -w3 image_masked.bmp | awk '{ b += b + $1 % 2 } ! (NR % 8) { printf("\\\\x%02x", b); b = 0 }' | xargs echo -ne
+```