4 Values whose Sum is 0+二分答案+POJ

4 Values whose Sum is 0

Time Limit: 15000MS		Memory Limit: 228000K
Total Submissions: 15284		Accepted: 4386
Case Time Limit: 5000MS

Description

The SUM problem can be formulated as follows: given four lists A, B, C, D of integer values, compute how many quadruplet (a, b, c, d ) ∈ A x B x C x D are such that a + b + c + d = 0 . In the following, we assume that all lists have the same size n .

Input

The first line of the input file contains the size of the lists n (this value can be as large as 4000). We then have n lines containing four integer values (with absolute value as large as 2 ²⁸ ) that belong respectively to A, B, C and D .

Output

For each input file, your program has to write the number quadruplets whose sum is zero.

Sample Input

6
-45 22 42 -16
-41 -27 56 30
-36 53 -37 77
-36 30 -75 -46
26 -38 -10 62
-32 -54 -6 45

Sample Output

5

解决方案：先两个两个一起，对其中一个排序，最后二分答案。

code：

#include
#include
#include
#include
#define MMAX 4004
using namespace std;
int A[MMAX],B[MMAX],C[MMAX],D[MMAX],AB[MMAX*MMAX],CD[MMAX*MMAX];
int n;
int main()
{
    while(~scanf("%d",&n))
    {
        for(int i=0; i0)
                {
                    high=mid;
                }
                else low=mid+1;
            }
            if((AB[low]+CD[i])!=0) low--;
            int temp=low;
            low=0,high=k-1;
            while(low=0)
                {
                    high=mid;
                }
                else low=mid+1;
            }
            low--;
            cnt+=(temp-low);

        }
        printf("%d\n",cnt);
    }
    return 0;
}