View Compilation Error

0_0_17198541_3915.cpp: In function 'bool cmp(node, node)':
0_0_17198541_3915.cpp:7:26: error: 'strcmp' was not declared in this scope
     return strcmp(a.s,b.s)<1;
                          ^
0_0_17198541_3915.cpp: In function 'int main()':
0_0_17198541_3915.cpp:25:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n) != -1){
                        ^
0_0_17198541_3915.cpp:29:33: error: 'strlen' was not declared in this scope
             int len = strlen(str);
                                 ^
0_0_17198541_3915.cpp:40:25: error: 'sort' was not declared in this scope
         sort(ss,ss+n,cmp);
                         ^
0_0_17198541_3915.cpp:43:40: error: 'strcmp' was not declared in this scope
             if(strcmp(ss[i].s,ss[i-1].s)!=0){
                                        ^
0_0_17198541_3915.cpp:47:26: error: 'printf' was not declared in this scope
         printf("%d\n",ans);
                          ^