Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k.
Example:
Given matrix = [
[1, 0, 1],
[0, -2, 3]
]
k = 2
The answer is 2. Because the sum of rectangle [[0, 1], [-2, 3]] is 2 and 2 is the max number no larger than k (k = 2).
Note:
The rectangle inside the matrix must have an area > 0.
What if the number of rows is much larger than the number of columns?
详见:https://leetcode.com/problems/max-sum-of-rectangle-no-larger-than-k/description/
C++:
class Solution {
public:
int maxSumSubmatrix(vector<vector<int>>& matrix, int k)
{
if (matrix.empty() || matrix[0].empty())
{
return 0;
}
int m = matrix.size(), n = matrix[0].size(), res = INT_MIN;
int sum[m][n];
for (int i = 0; i < m; ++i)
{
for (int j = 0; j < n; ++j)
{
int t = matrix[i][j];
if (i > 0)
{
t += sum[i - 1][j];
}
if (j > 0)
{
t += sum[i][j - 1];
}
if (i > 0 && j > 0)
{
t -= sum[i - 1][j - 1];
}
sum[i][j] = t;
for (int r = 0; r <= i; ++r)
{
for (int c = 0; c <= j; ++c)
{
int d = sum[i][j];
if (r > 0)
{
d -= sum[r - 1][j];
}
if (c > 0)
{
d -= sum[i][c - 1];
}
if (r > 0 && c > 0)
{
d += sum[r - 1][c - 1];
}
if (d <= k)
{
res = max(res, d);
}
}
}
}
}
return res;
}
};
参考:https://www.cnblogs.com/grandyang/p/5617660.html