View Compilation Error

0_0_22976246_21672.cpp: In function 'int p(char*)':
0_0_22976246_21672.cpp:4:23: error: 'strlen' was not declared in this scope
     int i,len=strlen(s);
                       ^
0_0_22976246_21672.cpp: In function 'void f(char*)':
0_0_22976246_21672.cpp:12:23: error: 'strlen' was not declared in this scope
     int i,len=strlen(s);
                       ^
0_0_22976246_21672.cpp: In function 'int main()':
0_0_22976246_21672.cpp:31:22: error: 'strcmp' was not declared in this scope
         if(strcmp(a,b)==0)
                      ^