View Compilation Error

0_0_35035289_26635.cpp:3:5: error: 'string' does not name a type
     string longestPalindrome(string s) {
     ^
0_0_35035289_26635.cpp:6:5: error: 'string' does not name a type
     string mlc(string ps) {
     ^
0_0_35035289_26635.cpp: In function 'int main()':
0_0_35035289_26635.cpp:86:25: error: 'scanf' was not declared in this scope
     while (~scanf("%s",a)){
                         ^
0_0_35035289_26635.cpp:87:26: error: 'class Solution' has no member named 'mlc'
         printf("%d\n",ss.mlc(a).length());
                          ^
0_0_35035289_26635.cpp:87:41: error: 'printf' was not declared in this scope
         printf("%d\n",ss.mlc(a).length());
                                         ^