“之”字形打印矩阵

【题目】

给定一个矩阵matrix，按照“之”字形的方式打印这个矩阵，例如：

1 2 3 4

5 6 7 8

9 10 11 12

“之”字形打印的结果为：1，2，5，9，6，3，4，7，10，11，8，12

【要求】

额外空间复杂度为O(1)。

 

 

package client;
import java.util.*;

public class Printer {
	private static int index = 0;
	public static void main(String[] args) {
		int[][] mat = {{85,40,61,54,9},{59,9,74,25,91},{68,97,33,91,91},{26,67,37,33,80},{24,8,19,32,65},{28,9,41,2,0},{4,41,48,99,9},{43,50,55,6,2},{95,30,8,62,1}};
		int[] printMatrix = printMatrix(mat, 9, 5);
		System.out.println(Arrays.toString(printMatrix));
	}
    public static int[] printMatrix(int[][] mat, int n, int m) {
    	int[] res = new int[mat.length*mat[0].length];
    	int tR = 0;
    	int tC = 0;
    	int dR = 0;
    	int dC = 0;
    	int endR = mat.length - 1;
    	int endC = mat[0].length - 1;
    	boolean fromUp = false;
    	while (tR != endR+1) {
    		printLevel(mat, tR, tC, dR, dC, fromUp, res);
    		tR = tC == endC ? tR + 1 : tR;
    		tC = tC == endC ? tC : tC + 1;
    		dC = dR == endR ? dC + 1 : dC;
    		dR = dR == endR ? dR : dR + 1;
    		fromUp = !fromUp;
    	}
    	return res;//[85, 40, 59, 68, 9, 61, 54, 74, 97, 26, 24, 67, 33, 25, 9, 91, 91, 37, 8, 28, 4, 9, 19, 33, 91, 80, 32, 41, 41, 43, 95, 50, 48, 2, 65, 0, 99, 55, 30, 8, 6, 9, 2, 62, 1]

    }

	private static void printLevel(int[][] mat, int tR, int tC, int dR, int dC,
			boolean fromUp, int[] res) {
		/*if (fromUp) {
			while (tR != dR + 1) {
				res[index++] = mat[tR++][tC--];
			}
		} else {
			while (dR != tR - 1) {
				res[index++] = mat[dR--][dC++];
			}
		}*/
		if (fromUp) {
			while (dC-1 != tC) {
				res[index++] = mat[tR++][tC--];
			}
		} else {
			while (dC != tC+1) {
				res[index++] = mat[dR--][dC++];
			}
		}
	}
}