foo.cc: In function 'void solve(char*, char*)':
foo.cc:20:14: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null]
     ans[j] = NULL;
              ^~~~
foo.cc: In function 'int main()':
foo.cc:27:5: error: 'scanf_s' was not declared in this scope
     scanf_s("%s", s, 1000);           //s为要处理的加密字符串，答案储存在ans里
     ^~~~~~~
foo.cc:27:5: note: suggested alternative: 'scanf'
     scanf_s("%s", s, 1000);           //s为要处理的加密字符串，答案储存在ans里
     ^~~~~~~
     scanf

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