Prefix 2D

import java.util.*;

public class Solution {
    static int[][] prefixSum(int[][] matrix) {
        int[][] ans = new int[matrix.length][matrix[0].length];

        ans[0][0] = matrix[0][0];
        for(int i = 1; i < matrix[0].length; i++) {
            // ans[0][i] = matrix[0][i] - matrix[0][i-1];
            ans[0][i] = matrix[0][i] + ans[0][i-1];
        }

        for(int i = 1; i < matrix.length; i++) {
            // ans[i][0] = matrix[i][0] - matrix[i-1][0];
            ans[i][0] = matrix[i][0] + ans[i-1][0];
        }

        for(int i = 1; i < matrix.length; i++) {
            for(int j = 1; j < matrix[0].length; j++) {
                ans[i][j] = matrix[i][j] + ans[i][j-1] + ans[i-1][j] - ans[i-1][j-1];
                // ans[i][j] = matrix[i][j] - (matrix[i][j-1] + matrix[i-1][j] - matrix[i-1][j-1]);
            }
        }

        return ans;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int m = sc.nextInt();
        int n = sc.nextInt();

        int[][] matrix = new int[m][n];

        for(int i = 0; i < m; i++) {
            for(int j = 0; j < n; j++) {
                matrix[i][j] = sc.nextInt();
            }
        }

        for(int[] mat: matrix)
            System.out.println(Arrays.toString(mat));

        int[][] prefixSum = prefixSum(matrix);

        for(int[] p: prefixSum)
            System.out.println(Arrays.toString(p));
        sc.close();
    }
}