【剑指offer】29.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.

思路

public int[] spiralOrder(int[][] matrix) {
        if (matrix.length == 0) return new int[0];
        int rows = matrix.length;
        int columns = matrix[0].length;
        int[] res = new int[rows * columns];
        int index = 0;


        int left = 0, right = columns - 1, top = 0, bottom = rows - 1;
        while (left <= right && top <= bottom) {
            // 从左向右
            for (int i = left; i <= right; i++) res[index++] = matrix[top][i];
            // 从上向下
            for (int i = top + 1; i <= bottom; i++) res[index++] = matrix[i][right];
            // 从右向左,考虑重复：上下两行相等的时候
            if (top != bottom)
                for (int i = right - 1; i >= left; i--) res[index++] = matrix[bottom][i];
            // 从下向上，考虑重复：左右两行相等的时候
            if (left != right)
                for (int i = bottom - 1; i > top; i--) res[index++] = matrix[i][left];
            left++; right--; top++; bottom--;
        }
        return res;
    }