View Compilation Error

0_0_16993517_12410.cpp: In function 'void createTrie(char*)':
0_0_16993517_12410.cpp:13:25: error: 'strlen' was not declared in this scope
     int len = strlen(str);
                         ^
0_0_16993517_12410.cpp: In function 'int findTrie(char*)':
0_0_16993517_12410.cpp:38:25: error: 'strlen' was not declared in this scope
     int len = strlen(str);
                         ^