View Compilation Error

0_0_15845669_15865.cpp: In function 'int main()':
0_0_15845669_15865.cpp:33:19: error: 'strlen' was not declared in this scope
   int len=strlen(s);
                   ^
0_0_15845669_15865.cpp:35:19: error: 'memset' was not declared in this scope
   memset(pre,0,len); pre[len-1]=s[len-1];
                   ^