View Compilation Error

0_0_19584855_7242.cpp: In function 'void insert(char*, node*)':
0_0_19584855_7242.cpp:24:25: error: 'strlen' was not declared in this scope
   int i,k,len=strlen(str);
                         ^
0_0_19584855_7242.cpp: In function 'int query(node*)':
0_0_19584855_7242.cpp:69:31: error: 'strlen' was not declared in this scope
   int i,cnt=0,k,len=strlen(str);
                               ^