Divide and conquer:4 Values whose Sum is 0(POJ 2785)

　　　　　　　　　　　　　　　　　

　　　　　　　　　　　　　　　　找四个数的和为0

　　题目大意：给定四个集合，要你每个集合选4个数字，组成和为0

　　这题是3977的简单版，只要和是0就可以了

　　

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <functional>
 4 #define MAX 4001
 5 
 6 using namespace std;
 7 
 8 typedef long long LL_INT;
 9 static LL_INT list[4][MAX], set_sum1[MAX*MAX];
10 
11 LL_INT *Binary_Lower_Bound(int &, LL_INT);
12 LL_INT *Binary_Upper_Bound(int &, LL_INT);
13 LL_INT solve(int &,int &);
14 
15 int main(void)
16 {
17     int list_contian, sum_comb;
18     LL_INT ans;
19 
20     while (~scanf("%d", &list_contian))
21     {
22         for (int i = 0; i < list_contian; i++)
23             scanf("%lld%lld%lld%lld", &list[0][i], &list[1][i], &list[2][i], &list[3][i]);
24 
25         sum_comb = 0;
26         for (int i = 0; i < list_contian; i++)//把第一张和第二张表的总数枚举出来
27             for (int j = 0; j < list_contian; j++)
28                 set_sum1[sum_comb++] = list[0][i] + list[1][j];
29 
30         sort(set_sum1, set_sum1 + sum_comb);
31         ans = solve(list_contian, sum_comb);
32         printf("%lld\n", ans);
33     }
34     return EXIT_SUCCESS;
35 }
36 
37 LL_INT solve(int &list_contain, int &sum_comb)
38 {
39     LL_INT tmp_sum, ans = 0;
40     int pos1, pos2;
41 
42     for (int i = 0; i < list_contain; i++)
43     {
44         for (int j = 0; j < list_contain; j++)
45         {
46             tmp_sum = -list[2][i] - list[3][j];
47             pos1 = Binary_Upper_Bound(sum_comb, tmp_sum) - set_sum1;
48             pos2 = Binary_Lower_Bound(sum_comb, tmp_sum) - set_sum1;
49             ans += pos1 - pos2;
50         }
51     }
52     return ans;
53 }
54 
55 LL_INT *Binary_Lower_Bound(int &sum_comb, LL_INT val)
56 {
57     int lb = 0, mid, count1 = sum_comb, count2;
58     while (count1 > 0)
59     {
60         count2 = count1 >> 1;
61         mid = lb + (count1 >> 1);
62         if (set_sum1[mid] < val)
63         {
64             lb = ++mid;
65             count1 -= count2 + 1;
66         }
67         else count1 = count2;
68     }
69     return &set_sum1[lb];
70 }
71 
72 LL_INT *Binary_Upper_Bound(int &sum_comb, LL_INT val)
73 {
74     int lb = 0, mid, count1 = sum_comb, count2;
75     while (count1 > 0)
76     {
77         count2 = count1 >> 1;
78         mid = lb + (count1 >> 1);
79         if (set_sum1[mid] <= val)
80         {
81             lb = ++mid;
82             count1 -= count2 + 1;
83         }
84         else count1 = count2;
85     }
86     return &set_sum1[lb];
87 }

　　

posted @ 2016-02-01 13:40  PhiliAI  阅读(221)  评论(0)  编辑  收藏  举报