foo.cc: In function 'void round(int, int)':
foo.cc:10:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < str.size(); ++i) {
                 ~~^~~~~~~~~~~~
foo.cc:15:16: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(w == left && l < right || l == left && w < right) {
      ~~~~~~~~~~^~~~~~~~~~~~
foo.cc:19:16: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(w >= left && l >= right || l >= left && w >= right) {
      ~~~~~~~~~~^~~~~~~~~~~~~
foo.cc:20:15: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    if(w == 10 && l == right || l == left && w == right) continue;
       ~~~~~~~~^~~~~~~~~~~~~

自豪的采用jd5进行评测(github.com/masnn/jd5)