/in/foo.c: In function 'countLetterPairs':
/in/foo.c:57:5: warning: implicit declaration of function 'qsort' [-Wimplicit-function-declaration]
     qsort(pairs, numPairs, sizeof(PairCount), comparePairs);
     ^~~~~
/in/foo.c: In function 'main':
/in/foo.c:67:22: warning: missing terminating " character
     str[strcspn(str, "
                      ^
/in/foo.c:68:1: warning: missing terminating " character
 ")] = '\0'; // 去掉换行符
 ^
/in/foo.c:73:0: error: unterminated argument list invoking macro "strcspn"
 }
 
/in/foo.c:67:5: error: expected ']' at end of input
     str[strcspn(str, "
     ^~~
/in/foo.c:67:8: error: array subscript is not an integer
     str[strcspn(str, "
        ^
/in/foo.c:67:5: error: expected declaration or statement at end of input
     str[strcspn(str, "
     ^~~