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GeezerVison is showing github.com — programming/problems/array/MaximumSumRectangleInMatrix.cpp at master · rp-code9/programming

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MaximumSumRectangleInMatrix.cpp

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MaximumSumRectangleInMatrix.cpp

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// GeeksforGeeks https://www.geeksforgeeks.org/maximum-sum-rectangle-in-a-2d-matrix-dp-27/
#include <iostream>
#include <vector>
#include <climits>
#include <algorithm>
struct Result
{
public:
int maxSum {INT_MIN};
int top {-1};
int bottom {-1};
int left {-1};
int right {-1};
void setValues(int sum, int t, int b, int l, int r) {
maxSum = sum;
top = t;
bottom = b;
left = l;
right = r;
}
};
int kadane(std::vector<int>& array, int& start, int& finish)
{
int currentSum {0};
int maxSum {INT_MIN};
int lStart {0};
finish = -1;
for (int i = 0; i < array.size(); ++i) {
currentSum += array[i];
if (currentSum < 0) {
currentSum = 0;
lStart = i + 1;
} else if (currentSum > maxSum) {
maxSum = currentSum;
finish = i;
start = lStart;
}
}
if (finish != - 1) {
return maxSum;
}
maxSum = array[0];
start = finish = 0;
for (int i = 1; i < array.size(); ++i) {
if (array[i] > maxSum) {
maxSum = array[i];
start = finish = i;
}
}
return maxSum;
}
void maximumSumRectangle(std::vector<std::vector<int>>& matrix, Result& result)
{
const int ROWS = matrix.size();
const int COLS = matrix[0].size();
int start {-1};
int finish {-1};
int sum {INT_MIN};
int maxSum {INT_MIN};
std::vector<int> temp(ROWS);
for (int left = 0; left < COLS; ++left) {
std::fill(temp.begin(), temp.end(), 0);
for (int right = left; right < COLS; ++right) {
// Find row sum of this vertical column at right index
for (int i = 0; i < ROWS; ++i) {
temp[i] = temp[i] + matrix[i][right];
}
// Run Kadane algorithm, get start and end indices
sum = kadane(temp, start, finish);
// Update bounds and max sum
if (sum > maxSum) {
maxSum = sum;
result.setValues(maxSum, start, finish, left, right);
}
}
}
}
void test(std::vector<std::vector<int>>& matrix)
{
struct Result result;
maximumSumRectangle(matrix, result);
std::cout << "Maximum sum is : " << result.maxSum << "\n";
std::cout << "(top, left) : " << "(" << result.top << "," << result.left << ")\n";
std::cout << "(bottom, right) : " << "(" << result.bottom << "," << result.right << ")\n";
}
int main()
{
std::vector<std::vector<int>> matrix = {{1, 2, -1, -4, 20},
{ -8, -3, 4, 2, 1},
{3, 8, 10, 1, 3},
{-4, -1, 1, 7, -6}};
test(matrix);
return 0;
}
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