POJ1054 枚举【STL__binary_search()_的应用】

①使用binary_search前要先保证有序

②binary_search函数仅返回true或false

③binary_search(first element, laste lment + 1, data to search)

 #include <stdio.h>
 #include <string.h>
 #include <math.h>
 #include <iostream>
 #include <algorithm>
 using namespace std;
 struct PLANT{
     int x, y;
 };
 PLANT map[];
 int r, c, num;
 int max_num;

 bool operator < (const PLANT & p1, const PLANT & p2){
     if(p1.x == p2.x)    return p1.y < p2.y;
     return p1.x < p2.x;
 }

 int function(int dx, int dy, int x, int y){
     int flag = ;
     while(x >=  && x <= r && y >=  && y <= c){
         PLANT temp;
         temp.x = x;
         temp.y = y;
         if(!binary_search(map, map+num, temp))  return ;
         x += dx;
         y += dy;
         ++flag;
     }
     return flag;
 }
 int main(){
     int i, j, k, t;
     int num_x, num_y;
     int flag;
     scanf("%d%d",&r,&c);
     scanf("%d",&num);
     for(i = ; i < num; ++i)    scanf("%d%d",&map[i].x,&map[i].y);

     sort(map, map+num);
     max_num = ;

     for(i = ; i < num; ++i){
         for(j = i + ; j < num; ++j){
             int dx = map[j].x - map[i].x;
             int dy = map[j].y - map[i].y;
             int px = map[i].x - dx;
             int py = map[i].y - dy;
             if(px >=  && px <= r && py >=  && py <= c)    continue;

             if(map[i].x + max_num * dx > r)   continue;
             int pY = map[i].y + max_num * dy;
             if(pY > c || pY < )    continue;

             px = dx + map[j].x;
             py = dy + map[j].y;
             int flag = ;
             while(px >=  && px <= r && py >=  && py <= c){
                 PLANT temp;
                 temp.x = px;
                 temp.y = py;
                 if(!binary_search(map, map+num, temp)){
                     flag = ;
                     break;
                 }
                 px += dx;
                 py += dy;
                 ++flag;
             }
             max_num = max(max_num, flag);
         }
     }
     if(max_num == )    printf("0\n");
     else    printf("%d\n",max_num);
     return ;
 }