View Compilation Error

0_0_19311678_28694.cpp: In function 'void createTrie(char*)':
0_0_19311678_28694.cpp:13:20: error: 'strlen' was not declared in this scope
  int len=strlen(str);
                    ^
0_0_19311678_28694.cpp: In function 'int findTrie(char*)':
0_0_19311678_28694.cpp:36:20: error: 'strlen' was not declared in this scope
  int len=strlen(str);
                    ^