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;
}