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 ;

 }