View Compilation Error

0_0_17154338_16861.cpp: In function 'void Creat_Trie(char*)':
0_0_17154338_16861.cpp:12:20: error: 'strlen' was not declared in this scope
      len=strlen(str);
                    ^
0_0_17154338_16861.cpp: In function 'int Find_Trie(char*)':
0_0_17154338_16861.cpp:33:19: error: 'strlen' was not declared in this scope
     len=strlen(str);
                   ^
0_0_17154338_16861.cpp: In function 'int main()':
0_0_17154338_16861.cpp:51:29: error: 'memset' was not declared in this scope
     memset(str,0,sizeof(str));
                             ^