View Compilation Error

0_0_34092934_26784.cpp: In function 'int main()':
0_0_34092934_26784.cpp:8:22: error: 'memset' was not declared in this scope
  memset(b,0,sizeof(b));
                      ^
0_0_34092934_26784.cpp:11:21: error: 'strlen' was not declared in this scope
   int i,len=strlen(a);
                     ^
0_0_34092934_26784.cpp:30:12: error: 'k' was not declared in this scope
       if(j<k)
            ^
0_0_34092934_26784.cpp:35:11: error: 'k' was not declared in this scope
      if(j<k)
           ^