hdu 4631Sad Love Story<计算几何>

链接：http://acm.hdu.edu.cn/showproblem.php?pid=4631

题意：依次给你n个点，每次求出当前点中的最近点对，输出所有最近点对的和；

思路：按照x排序，然后用set维护，每次插入只更新当前点和插入点前后几个位置~

 1 #include <iostream>

 2 #include <cstdio>

 3 #include <cmath>

 4 #include <algorithm>

 5 #include <vector>

 6 #include <set>

 7 using namespace std;

 8 const int MAX=5e5+10;

 9 typedef long long LL;

10 LL ax, bx, cx, ay, by, cy;

11 int T, N;

12 struct Point

13 {

14     LL x, y;

15     Point(){}

16     Point(LL a, LL b):x(a), y(b){};

17    bool operator < (const Point &p)const{

18         return x < p.x || (x == p.x && y < p.y);

19     }

20 

21 }p[MAX];

22 LL sqr(LL x)

23 {

24     return x*x;

25 }

26 LL Dis( Point A, Point B )

27 {

28     return sqr(A.x-B.x)+sqr(A.y-B.y);

29 }

30 

31 void Init( )

32 {

33     LL xx=0, yy=0;

34     for( int i=0; i<N; ++ i ){

35         xx=(xx*ax+bx)%cx;

36         yy=(yy*ay+by)%cy;

37         p[i]=Point( xx, yy );

38     }

39 }

40 multiset<Point>st;

41 multiset<Point>::iterator it1, it2, it3;

42 void gao(){

43     st.clear();

44     LL ans = 0;

45     st.insert(p[0]);

46     LL mi = 1LL<<60;

47     for (int i = 1; i < N; i++){

48         Point t = p[i];

49         st.insert(t);

50         it1 = it2 = it3 = st.lower_bound(t);

51         int k = 5;

52         while (k--){

53             if (it1 != st.begin()) it1--;

54             if (it3 != it1){

55                 LL d1 = Dis(t,*it1);

56                 if (d1<mi){

57                     mi = d1;

58                 }

59             }

60             if (it2 != st.end()) it2++;

61             if (it2 != st.end() && it2!= it3){

62                 LL d2 = Dis(t,*it2);

63                 if (d2 < mi){

64                     mi = d2;

65                 }

66             }

67         }

68         ans += mi;

69         if (mi == 0) break;

70     }

71     printf("%I64d\n",ans);

72 }

73 int main()

74 {

75     scanf("%d", &T);

76     while(T--){

77         scanf("%d", &N);

78         scanf("%I64d%I64d%I64d%I64d%I64d%I64d", &ax, &bx, &cx, &ay, &by, &cy);

79         Init();

80         gao();

81     }

82     return 0;

83 }

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