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)

 1 #include <stdio.h>
 2 #include <string.h>
 3 #include <math.h>
 4 #include <iostream>
 5 #include <algorithm>
 6 using namespace std;
 7 struct PLANT{
 8     int x, y;
 9 };
10 PLANT map[5001];
11 int r, c, num;
12 int max_num;
13
14 bool operator < (const PLANT & p1, const PLANT & p2){
15     if(p1.x == p2.x)    return p1.y < p2.y;
16     return p1.x < p2.x;
17 }
18
19 int function(int dx, int dy, int x, int y){
20     int flag = 2;
21     while(x >= 1 && x <= r && y >= 1 && y <= c){
22         PLANT temp;
23         temp.x = x;
24         temp.y = y;
25         if(!binary_search(map, map+num, temp))  return 0;
26         x += dx;
27         y += dy;
28         ++flag;
29     }
30     return flag;
31 }
32 int main(){
33     int i, j, k, t;
34     int num_x, num_y;
35     int flag;
36     scanf("%d%d",&r,&c);
37     scanf("%d",&num);
38     for(i = 0; i < num; ++i)    scanf("%d%d",&map[i].x,&map[i].y);
39
40     sort(map, map+num);
41     max_num = 2;
42
43     for(i = 0; i < num; ++i){
44         for(j = i + 1; j < num; ++j){
45             int dx = map[j].x - map[i].x;
46             int dy = map[j].y - map[i].y;
47             int px = map[i].x - dx;
48             int py = map[i].y - dy;
49             if(px >= 1 && px <= r && py >= 1 && py <= c)    continue;
50
51             if(map[i].x + max_num * dx > r)   continue;
52             int pY = map[i].y + max_num * dy;
53             if(pY > c || pY < 1)    continue;
54
55             px = dx + map[j].x;
56             py = dy + map[j].y;
57             int flag = 2;
58             while(px >= 1 && px <= r && py >= 1 && py <= c){
59                 PLANT temp;
60                 temp.x = px;
61                 temp.y = py;
62                 if(!binary_search(map, map+num, temp)){
63                     flag = 0;
64                     break;
65                 }
66                 px += dx;
67                 py += dy;
68                 ++flag;
69             }
70             max_num = max(max_num, flag);
71         }
72     }
73     if(max_num == 2)    printf("0\n");
74     else    printf("%d\n",max_num);
75     return 0;
76 }

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