剑指offer-顺时针打印矩阵

题目描述

输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下4 X 4矩阵： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 则依次打印出数字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

 

首先判断需要走几圈，然后每圈依次按照向右向下向左向上的顺序遍历

public ArrayList<Integer> printMatrix(int [][] matrix) {//my
       int rowlength = matrix.length;
        int collength = matrix[0].length;
        int count = ((rowlength<collength?rowlength:collength)-1)/2+1;
        ArrayList<Integer> result  = new ArrayList<Integer>();
        for (int i = 0; i < count; i++) {
            for (int j = i; j < collength-i; j++) {//向右
                result.add(matrix[i][j]);
            }
            for (int j = i+1; j < rowlength-i; j++) {//向下
                result.add(matrix[j][collength-i-1]);
            }
            for (int j = collength-i-2; j >= i&&(rowlength-i-1)>i; j--) {//向左 注意判断i的值
                result.add(matrix[rowlength-i-1][j]);
            }
            for (int j = rowlength-i-2; j > i &&(collength-i-1)>i; j--) {//向上 注意判断i的值
                result.add(matrix[j][i]);
            }
        }
        return result;
    }