11、矩阵运算
已知一个大小为 n x m 的矩阵 matrixA，计算出一个和矩阵 matrixA 具有相同维度的矩阵 matrixB（即矩阵 matrixB 的大小也为 n x m），而矩阵 matrixB 中的每个元素 matrixB[i, j] 都对应了矩阵 matrixA 中元素 matrixA[i, j] 左上方（包含 matrixA[i, j] ）的所有元素之和。

public class MatrixCal {public static void main(String[] args) {int[][] matrixA = {{3,7,1},{2,4,0},{9,4,2}};Solution solution = new Solution();int[][] matrixB = solution.matrixCalF(matrixA);for (int i = 0; i < matrixA.length; i++) {for (int j = 0; j < matrixA[0].length; j++) {System.out.print(matrixB[i][j] + " ");}System.out.println();}}static class Solution{public int[][] matrixCalF(int[][] matrixA) {if(matrixA == null) {return null;}int NL = matrixA.length;int MC = matrixA[0].length;int[][] matrixB = new int[NL][MC];matrixB[0][0] = matrixA[0][0];for (int iL = 0; iL < NL; iL++) {for (int jC = 0; jC < MC; jC++) {int linCount = 0;int colCount = 0;for (int k = 0; k <= jC; k++ ) {linCount += matrixA[iL][k];}for (int l = 0; l <= iL; l++) {colCount += matrixA[l][jC];}if(iL == 0 && jC > 0) {matrixB[iL][jC] = linCount;} else if(iL > 0 && jC == 0){matrixB[iL][jC] = colCount;} else if(iL > 0 && jC > 0) {matrixB[iL][jC] = matrixB[iL-1][jC-1] + linCount + colCount - matrixA[iL][jC];} else {continue;}}}return matrixB;}}
//    static class Solution{
//        public int[][] matrixCalF(int[][] matrixA) {
//            if(matrixA == null) {
//                return null;
//            }
//            int NL = matrixA.length;
//            int ML = matrixA[0].length;
//            int[][] matrixB = new int[NL][ML];
//            for (int i = 0; i < NL; i++) {
//                for (int j = 0; j < ML; j++) {
//                    for (int k = 0; k <= i; k++ ) {
//                        for (int l = 0; l <= j; l++)
//                            matrixB[i][j] += matrixA[k][l];
//                    }
//                }
//            }
//            return matrixB;
//        }
//    }
}