View Compilation Error

0_0_20155815_10758.cpp: In function 'void build(char*, int*)':
0_0_20155815_10758.cpp:16:26: error: 'strlen' was not declared in this scope
     int length=strlen(str);
                          ^
0_0_20155815_10758.cpp: In function 'int main()':
0_0_20155815_10758.cpp:25:38: error: 'memset' was not declared in this scope
         memset(tree1,-1,sizeof(tree1));
                                      ^