View Compilation Error

0_0_19231463_13406.cpp: In function 'void insert(char*, int)':
0_0_19231463_13406.cpp:16:21: error: 'strlen' was not declared in this scope
    int len=strlen(ss);  
                     ^
0_0_19231463_13406.cpp: In function 'int search(char*)':
0_0_19231463_13406.cpp:36:20: error: 'strlen' was not declared in this scope
   int len=strlen(ch);  
                    ^
0_0_19231463_13406.cpp: In function 'int main()':
0_0_19231463_13406.cpp:63:28: error: 'strlen' was not declared in this scope
     for(int j=0;j<strlen(ss);++j)  
                            ^