二维数组中，值最大的连续子数组

// Program to find maximum sum subarray in a given 2D array
#include <stdio.h>
#include <string.h>
#include <limits.h>
#define ROW 4
#define COL 5

// Implementation of Kadane's algorithm for 1D array. The function returns the
// maximum sum and stores starting and ending indexes of the maximum sum subarray
// at addresses pointed by start and finish pointers respectively.
int kadane(int* arr, int* start, int* finish, int n)
{
// initialize sum, maxSum and start
int sum = 0, maxSum = INT_MIN, i;

// needed if sum NEVER becomes less than 0
*start = 0;

// Standard Kadane's algorithm. See following link
// http://www.geeksforgeeks.org/largest-sum-contiguous-subarray/ for (i = 0; i < n; ++i)
{
sum += arr[i];
if (sum < 0)
{
sum = 0;
*start = i+1;
}
else if (sum > maxSum)
{
maxSum = sum;
*finish = i;
}
}
return maxSum;
}

// The main function that finds maximum sum rectangle in M[][]
void findMaxSum(int M[][COL])
{
// Variables to store the final output
int maxSum = 0, finalLeft, finalRight, finalTop, finalBottom;

int left, right, i;
int temp[ROW], sum, start, finish;

// Set the left column
for (left = 0; left < COL; ++left)
{
// Initialize all elements of temp as 0
memset(temp, 0, sizeof(temp));

// Set the right column for the left column set by outer loop
for (right = left; right < COL; ++right)
{
// Calculate sum between current left and right for every row 'i'
for (i = 0; i < ROW; ++i)
temp[i] += M[i][right];

// Find the maximum sum subarray in temp[]. The kadane() function
// also sets values of start and finish.  So 'sum' is sum of
// rectangle between (start, left) and (finish, right) which is the
//  maximum sum with boundary columns strictly as left and right.
sum = kadane(temp, &start, &finish, ROW);

// Compare sum with maximum sum so far. If sum is more, then update
// maxSum and other output values
if (sum > maxSum)
{
maxSum = sum;
finalLeft = left;
finalRight = right;
finalTop = start;
finalBottom = finish;
}
}
}

// Print final values
printf("(Top, Left) (%d, %d)\n", finalTop, finalLeft);
printf("(Bottom, Right) (%d, %d)\n", finalBottom, finalRight);
printf("Max sum is: %d\n", maxSum);
}

// Driver program to test above functions
int main()
{
int M[ROW][COL] = {{1, 2, -1, -4, -20},
{-8, -3, 4, 2, 1},
{3, 8, 10, 1, 3},
{-4, -1, 1, 7, -6}
};

findMaxSum(M);

return 0;
}