HDU OJ Matrix Swapping II

Matrix Swapping II

Time Limit : 9000/3000ms (Java/Other)   Memory Limit : 32768/32768K (Java/Other)

Total Submission(s) : 12   Accepted Submission(s) : 8

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Problem Description

Given an N * M matrix with each entry equal to 0 or 1. We can find some rectangles in the matrix whose entries are all 1, and we define the maximum area of such rectangle as this matrix’s goodness.
We can swap any two columns any times, and we are to make the goodness of the matrix as large as possible.

Input

There are several test cases in the input. The first line of each test case contains two integers N and M (1 ≤ N,M ≤ 1000). Then N lines follow, each contains M numbers (0 or 1), indicating the N * M matrix

Output

Output one line for each test case, indicating the maximum possible goodness.

Sample Input

3 4
1011
1001
0001
3 4
1010
1001
0001

Sample Output

4
2

分析：对每一行进行处理然后再叠加，到每一行用sum[j]记下到这一行有多少个1

例如：

1 0 1 1 sum[j]的记录就是： 1 0 1 1

1 0 0 1                             2 0 0 2

0 0 0 1                             0 0 0 3

然后对num[j]从大到小排一下，求出读取到当前行能够得到的最大面积。

也就是最右边放着最多的1，依次类推。那么当前最大的面积就是 MAX（max,sum[j]*(j+1)）了