poj1050

To the Max

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 39081		Accepted: 20639

Description

Given a two-dimensional array of positive and negative integers, a sub-rectangle is any contiguous sub-array of size 1*1 or greater located within the whole array. The sum of a rectangle is the sum of all the elements in that rectangle. In this problem the sub-rectangle with the largest sum is referred to as the maximal sub-rectangle.
As an example, the maximal sub-rectangle of the array:

0 -2 -7 0

9 2 -6 2

-4 1 -4 1

-1 8 0 -2

is in the lower left corner:

9 2

-4 1

-1 8

and has a sum of 15.

Input

The
input consists of an N * N array of integers. The input begins with a
single positive integer N on a line by itself, indicating the size of
the square two-dimensional array. This is followed by N^2 integers
separated by whitespace (spaces and newlines). These are the N^2
integers of the array, presented in row-major order. That is, all
numbers in the first row, left to right, then all numbers in the second
row, left to right, etc. N may be as large as 100. The numbers in the
array will be in the range [-127,127].

Output

Output the sum of the maximal sub-rectangle.

Sample Input

4
0 -2 -7 0 9 2 -6 2
-4 1 -4  1 -1

8  0 -2

Sample Output

15

 /*
  * File:   main.cpp
  * Author: liaoyu <liaoyu@whu.edu.cn>
  *
  * Created on April 1, 2014, 5:34 PM
  */

 #include <iostream>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <cmath>
 #include <algorithm>
 using namespace std;

 int a[][];

 int maxSubArray(int n, int* a)
 {
     int max = 0x80000000;
     int b = a[];
     for (int i = ; i < n; i++) {
         if (b > )b += a[i];
         else b = a[i];
         if (b > max)max = b;
     }
     return max;
 }
 int b[];

 int main()
 {
     int n;
     scanf("%d", &n);
     int max = 0x80000000;
     for (int i = ; i < n; i++)
         for (int j = ; j < n; j++)
             scanf("%d", &a[i][j]);
     for (int i = ; i < n; i++)
         for (int j = i; j < n; j++) {
             for (int l = ; l < n; l++) {
                 b[l] = ;
                 for (int k = i; k <= j; k++) {
                     b[l] += a[l][k];
                 }
             }
             int tmp = maxSubArray(n, b);
             if (tmp > max)max = tmp;
         }
     printf("%d\n", max);
 }