View Compilation Error

0_0_37383766_15300.cpp: In function 'void insert(char*)':
0_0_37383766_15300.cpp:10:21: error: 'strlen' was not declared in this scope
     int len=strlen(w);
                     ^
0_0_37383766_15300.cpp: In function 'int search(char*)':
0_0_37383766_15300.cpp:23:21: error: 'strlen' was not declared in this scope
     int len=strlen(w);
                     ^
0_0_37383766_15300.cpp: In function 'int main()':
0_0_37383766_15300.cpp:42:14: error: 'i' was not declared in this scope
  for(int n=0;i<=4;n++){
              ^