View Compilation Error

0_0_20981659_1742.cpp: In function 'int main()':
0_0_20981659_1742.cpp:52:25: error: 'scanf' was not declared in this scope
     while(scanf("%s",str) != -1){
                         ^
0_0_20981659_1742.cpp:53:25: error: 'printf' was not declared in this scope
         printf("%s ",str);
                         ^
0_0_20981659_1742.cpp:55:29: error: 'strlen' was not declared in this scope
         int len = strlen(str);
                             ^
0_0_20981659_1742.cpp:69:32: error: 'memset' was not declared in this scope
         memset(dp,-1,sizeof(dp));
                                ^