编程之美子矩阵之和的最大值

把二维转化为一维,再利用求最大子序列的方法求最大子矩阵.

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<assert.h>

#define max(a, b) ((a) > (b) ? (a) : (b))

const int neginf = 0x80000001;

int a[100][100] = {0};

int getMaxSum(int *b, int n)
{
	int curSum = 0;
	int maxSum = neginf;
	for(int i=0; i<n; i++)
	{
		if(curSum < 0)
			curSum = 0;
		curSum += b[i];
		maxSum = max(maxSum, curSum);
	}
	return maxSum;
}

int * getSeqMatrix(int s, int e, int n)
{
	int *b = new int[n];
	for(int i=0; i<n; i++)
		b[i] = 0;
	for(i=0; i<n; i++)
	{
		for(int j=s; j<=e; j++)
		{
			b[i] += a[j][i];
		}
	}
	return b;
}

int getMaxMatrix(int n)
{
	int curSum = 0;
	int maxSum = neginf;
	for(int i=0; i<n; i++)
	{
		for(int j=i; j<n; j++)
		{
			int *b = getSeqMatrix(i, j, n);
			curSum = getMaxSum(b, n);
			maxSum = max(curSum, maxSum);
			delete []b;
		}
	}
	return maxSum;
}

void test()
{
	int n;
	while(scanf("%d", &n)!=EOF)
	{
		if(n == 0) break;
		for(int i=0; i<n; i++)
		{
			for(int j=0; j<n; j++)
				scanf("%d", &a[i][j]);
		}
		int ret = getMaxMatrix(n);
		printf("%d\n", ret);
	}
}

int main()
{
	test();
	return 0;
}