
public class LeetCode0363 {
	public int maxSumSubmatrix(int[][] matrix, int k) {
		int m = matrix.length, n = matrix[0].length, ans = Integer.MIN_VALUE;
		long[] sum = new long[m + 1];
		for (int i = 0; i < n; ++i) {
			long[] sumInRow = new long[m];
			for (int j = i; j < n; ++j) {
				for (int p = 0; p < m; ++p) {
					sumInRow[p] += matrix[p][j];
					sum[p + 1] = sum[p] + sumInRow[p];
				}
				ans = Math.max(ans, mergeSort(sum, 0, m + 1, k));
				if (ans == k)
					return k;
			}
		}
		return ans;
	}

	int mergeSort(long[] sum, int start, int end, int k) {
		if (end == start + 1)
			return Integer.MIN_VALUE;
		int mid = start + (end - start) / 2, cnt = 0;
		int ans = mergeSort(sum, start, mid, k);
		if (ans == k)
			return k;
		ans = Math.max(ans, mergeSort(sum, mid, end, k));
		if (ans == k)
			return k;
		long[] cache = new long[end - start];
		for (int i = start, j = mid, p = mid; i < mid; ++i) {
			while (j < end && sum[j] - sum[i] <= k){
				++j;
			}
				
			if (j - 1 >= mid) {
				ans = Math.max(ans, (int) (sum[j - 1] - sum[i]));
				if (ans == k){
					return k;
				}
			}
			while (p < end && sum[p] < sum[i]){
				cache[cnt++] = sum[p++];
			}
				
			cache[cnt++] = sum[i];
		}
		System.arraycopy(cache, 0, sum, start, cnt);
		return ans;
	}
}

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