View Compilation Error

0_0_20969359_22260.cpp: In function 'void rev(int)':
0_0_20969359_22260.cpp:28:27: error: 'swap' was not declared in this scope
     swap(sum0[id],sum1[id]);
                           ^
0_0_20969359_22260.cpp: In function 'int main()':
0_0_20969359_22260.cpp:60:29: error: 'scanf' was not declared in this scope
     while(scanf("%d%d",&n,&k) && (n+k)){
                             ^
0_0_20969359_22260.cpp:64:31: error: 'strlen' was not declared in this scope
         int len = strlen(str+1);
                               ^
0_0_20969359_22260.cpp:72:25: error: 'printf' was not declared in this scope
             printf("0\n");
                         ^
0_0_20969359_22260.cpp:76:31: error: 'printf' was not declared in this scope
             if(ok)printf("0\n");
                               ^
0_0_20969359_22260.cpp:77:31: error: 'printf' was not declared in this scope
             else printf("-1\n");
                               ^
0_0_20969359_22260.cpp:95:30: error: 'printf' was not declared in this scope
                 printf("-1\n");
                              ^
0_0_20969359_22260.cpp:97:34: error: 'printf' was not declared in this scope
                 printf("%d\n",ans);
                                  ^