View Compilation Error

0_0_17020062_5029.cpp: In function 'void SplitExp(char*)':
0_0_17020062_5029.cpp:35:20: error: 'strlen' was not declared in this scope
  for(i=0;i<strlen(s);i++)
                    ^
0_0_17020062_5029.cpp: In function 'double Cal()':
0_0_17020062_5029.cpp:75:21: error: 'strlen' was not declared in this scope
  int len=strlen(post);
                     ^
0_0_17020062_5029.cpp: In function 'int main()':
0_0_17020062_5029.cpp:112:18: error: 'strcmp' was not declared in this scope
   if(strcmp(e,"0")==0)
                  ^