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 "); 74 else printf("%d ",max_num); 75 return 0; 76 }