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

　　

 #include <iostream>
 #include <algorithm>
 #include <functional>
 #define MAX 4001

 using namespace std;

 typedef long long LL_INT;
 static LL_INT list[][MAX], set_sum1[MAX*MAX];

 LL_INT *Binary_Lower_Bound(int &, LL_INT);
 LL_INT *Binary_Upper_Bound(int &, LL_INT);
 LL_INT solve(int &,int &);

 int main(void)
 {
     int list_contian, sum_comb;
     LL_INT ans;

     while (~scanf("%d", &list_contian))
     {
         for (int i = ; i < list_contian; i++)
             scanf("%lld%lld%lld%lld", &list[][i], &list[][i], &list[][i], &list[][i]);

         sum_comb = ;
         for (int i = ; i < list_contian; i++)//把第一张和第二张表的总数枚举出来
             for (int j = ; j < list_contian; j++)
                 set_sum1[sum_comb++] = list[][i] + list[][j];

         sort(set_sum1, set_sum1 + sum_comb);
         ans = solve(list_contian, sum_comb);
         printf("%lld\n", ans);
     }
     return EXIT_SUCCESS;
 }

 LL_INT solve(int &list_contain, int &sum_comb)
 {
     LL_INT tmp_sum, ans = ;
     int pos1, pos2;

     for (int i = ; i < list_contain; i++)
     {
         for (int j = ; j < list_contain; j++)
         {
             tmp_sum = -list[][i] - list[][j];
             pos1 = Binary_Upper_Bound(sum_comb, tmp_sum) - set_sum1;
             pos2 = Binary_Lower_Bound(sum_comb, tmp_sum) - set_sum1;
             ans += pos1 - pos2;
         }
     }
     return ans;
 }

 LL_INT *Binary_Lower_Bound(int &sum_comb, LL_INT val)
 {
     int lb = , mid, count1 = sum_comb, count2;
     while (count1 > )
     {
         count2 = count1 >> ;
         mid = lb + (count1 >> );
         if (set_sum1[mid] < val)
         {
             lb = ++mid;
             count1 -= count2 + ;
         }
         else count1 = count2;
     }
     return &set_sum1[lb];
 }

 LL_INT *Binary_Upper_Bound(int &sum_comb, LL_INT val)
 {
     int lb = , mid, count1 = sum_comb, count2;
     while (count1 > )
     {
         count2 = count1 >> ;
         mid = lb + (count1 >> );
         if (set_sum1[mid] <= val)
         {
             lb = ++mid;
             count1 -= count2 + ;
         }
         else count1 = count2;
     }
     return &set_sum1[lb];
 }