View Compilation Error

0_0_15323088_3461.cpp: In function 'int main()':
0_0_15323088_3461.cpp:18:27: error: 'strcmp' was not declared in this scope
    if(strcmp(arr[i],arr[j])==0)
                           ^
0_0_15323088_3461.cpp:28:28: error: 'strcmp' was not declared in this scope
   if(strcmp(arr[i+1],arr[i])==0)
                            ^
0_0_15323088_3461.cpp:31:28: error: 'strlen' was not declared in this scope
  for(i=0;i<strlen(arr[temp]);i++)
                            ^