/in/foo.cc: In function 'int main()':
/in/foo.cc:10:44: warning: unused variable 'j' [-Wunused-variable]
  int a[5000]={0},b[5000]={0},c[5000]={0},i,j,len,temp; //len 输入的两个字符串长度的最大值  
                                            ^
/in/foo.cc:43:17: warning: 'temp' may be used uninitialized in this function [-Wmaybe-uninitialized]
   c[i]=a[i]+b[i]+temp;
        ~~~~~~~~~^~~~~