foo.cpp: In function 'int compare(const void*, const void*)':
foo.cpp:13:33: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  ((pNode)a)->x == ((pNode)b)->x && ((pNode)a)->y > ((pNode)b)->y;
                                 ^
foo.cpp: In function 'int main()':
foo.cpp:70:28: error: 'memset' was not declared in this scope
  memset(ans,n*sizeof(int),0);
                            ^
foo.cpp:59:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,n,m;
        ^
foo.cpp:59:12: warning: unused variable 'm' [-Wunused-variable]
  int i,j,n,m;
            ^