View Compilation Error

0_0_25682213_24186.cpp: In function 'void createTrie(char*)':
0_0_25682213_24186.cpp:12:20: error: 'strlen' was not declared in this scope
  int len=strlen(str);
                    ^
0_0_25682213_24186.cpp: In function 'int findTrie(char*)':
0_0_25682213_24186.cpp:35:20: error: 'strlen' was not declared in this scope
  int len=strlen(str);
                    ^