之字形打印矩阵

思路：在（0,0）处，设置两个点，一个点a,一个点b,a和b同时移动，a向右移动，移到边界后向下移动，b向下移动，移动边界后向右移动，结束条件是a或者b到达矩阵的右下顶点，每次移动后就打印ab两点连线

public class ZigZagPrintMatrix {

    public static void main(String[] args) {

        int[][] matrix = { { 1,  2,  3,   4  , 20 }, 
                           { 5,  6,  7,   8  , 21 },
                           { 9,  10, 11,  12 , 22 },
                           { 13, 14, 15, 16 , 23 } };
        print(matrix);
        //printLine(matrix,2,3,3,2,true);
    }

    public static void print(int[][] matrix) {
        int aR = 0;
        int aC = 0;
        int bR = 0;
        int bC = 0;
        boolean flag = false;
        while (aR != matrix.length || bC != matrix[0].length) {
            // System.out.println("(" +aR +","+ aC + ") " + "(" +bR+","+ bC + ") " );
            // 先打印
            printLine(matrix, aR, aC, bR, bC, flag);
            if (aR == 0 && aC < matrix[0].length - 1) { // 列逐渐增加
                aC += 1;
            } else if (aR == 0 && aC == matrix[0].length - 1) { // 到达顶点后行增加
                aR += 1;
            } else { // 行继续增加,直到aR = matrix.length跳出循环
                aR += 1;
            }
            if (bC == 0 && bR < matrix.length - 1) {
                bR += 1;
            } else if (bC == 0 && bR == matrix.length - 1) {
                bC++;
            } else {
                bC++;
            }
            flag = !flag;
        }
    }

    private static void printLine(int[][] matrix, int aR, int aC, int bR, int bC, boolean flag) {
        if (flag) { // 从右上向左下打印
            while (aR <= bR) {
                System.out.print(matrix[aR++][aC--] + " ");
            }
        } else { // 从左下向右上打印
            while (bC <= aC) {
                System.out.print(matrix[bR--][bC++] + " ");
            }
        }
    }
}