foo.cc:10:1: error: 'string' does not name a type; did you mean 'stdin'?
 string m;
 ^~~~~~
 stdin
foo.cc:11:9: error: 'string' was not declared in this scope
 bool hw(string a) { //判断回文
         ^~~~~~
foo.cc:11:9: note: suggested alternative: 'stdin'
 bool hw(string a) { //判断回文
         ^~~~~~
         stdin
foo.cc:16:1: error: 'string' does not name a type; did you mean 'stdin'?
 string add(int k, string b) { //高精度加法过程，推广到 k 进制
 ^~~~~~
 stdin
foo.cc: In function 'int main()':
foo.cc:41:2: error: 'cin' was not declared in this scope
  cin >> n >> m;
  ^~~
foo.cc:41:2: note: suggested alternative: 'main'
  cin >> n >> m;
  ^~~
  main
foo.cc:41:14: error: 'm' was not declared in this scope
  cin >> n >> m;
              ^
foo.cc:43:10: error: 'hw' cannot be used as a function
   if(hw(m)) { //如果是回文数就输出步骤数
          ^
foo.cc:47:12: error: 'add' was not declared in this scope
   else m = add(n, m);
            ^~~
foo.cc:47:12: note: suggested alternative: 'rand'
   else m = add(n, m);
            ^~~
            rand

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