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 }