面试题4（剑指）-螺旋打印矩阵

题目

n阶矩阵，螺旋打印出来

思路

需要控制：1.边界 2.方向

使用一个二维数组存放数据，数组初始化为0，数组共有n平方个元素，因为是从1开始，所以元素的值是从1到n×n。每次填入一个数字判断一次方向和边界

实现

package lms.algorithm.offer;

//螺旋打印矩阵
public class SpiralMatrix {
    public static int[][] createMatrix(int n){
        int[][] matrix = new int[n][n];
        int right = 1, down = 2, left = 3, up = 4;
        int direction = right;

        int numb = n * n;
        int i = 0, j = 0;
        for (int p = 1; p <= numb; p++){
            matrix[i][j] = p;

            if (direction == right){
                if (j + 1 < n && matrix[i][j + 1] == 0){
                    j++;
                }else {
                    i++;
                    direction = down;
                    continue;
                }
            }
            if (direction == down){
                if (i + 1 < n && matrix[i+1][j] == 0){
                    i++;
                }else {
                    j--;
                    direction = left;
                    continue;
                }
            }
            if (direction == left){
                if (j - 1 >= 0 && matrix[i][j-1] == 0){
                    j--;
                }else {
                    i--;
                    direction = up;
                    continue;
                }
            }
            if (direction == up){
                if (i - 1 >= 0 && matrix[i-1][j] == 0){
                    i--;
                }else {
                    j++;
                    direction = right;
                    continue;
                }
            }
        }
        return matrix;
    }

    public static void main(String[] args) {
        int[][] n = createMatrix(6);
        for (int i=0;i<n.length;i++){
            for (int j=0;j<n[i].length;j++){
                System.out.print(n[i][j] + " ");
            }
            System.out.println("");
        }
    }
}

运行结果

1 2 3 4 5 6
20 21 22 23 24 7
19 32 33 34 25 8
18 31 36 35 26 9
17 30 29 28 27 10
16 15 14 13 12 11