顺时针打印矩阵

思路

参考视频

题解

注意边界条件

JAVA判断二维数组是否空

1、二维数组首地址是否为空，即array==null；

2、二维数组是否为{}，即array.length==0的情况；

3、二维数组是否为{{}}，即array.length=1&&array[0].length==0的情况；

        if((matrix==null||matrix.length==0)||(matrix.length==1&&matrix[0].length==0)){
            int []a = {};
            System.out.println("空数组");
            return a;
        }

左、下、右、上四条变上的循环

package swordPointingToTheOffer;

public class TwentyNine {

    public static int[] spiralOrder(int[][] matrix) {
        if((matrix==null||matrix.length==0)||(matrix.length==1&&matrix[0].length==0)){
            int []a = {};
            System.out.println("空数组");
            return a;
        }
        int top = 0;
        int buttom = matrix.length-1;
        int left = 0;
        int right = matrix[0].length-1;
        int pi = 0,pj = 0;
        int [] res=new int[(buttom+1)*(right+1)];
        int pos =0;
        int total = matrix.length*matrix[0].length;
        while (true){
            if(pos>=total){
                break;
            }
            while (pj<matrix[0].length){
                int result = matrix[pi][pj];
                res[pos] = result;
                pos++;
                pj++;
                if(pj>right){
                    pj--;
                    right--;
                    pi++;
                    break;
                }
            }
            if(pos>=total){
                break;
            }
            while (pi<matrix.length){
                int result = matrix[pi][pj];
                res[pos] = result;
                pos++;
                pi++;
                if(pi>buttom){
                    pi--;
                    buttom--;
                    pj--;
                    break;
                }
            }
            if(pos>=total){
                break;
            }
            while (pj>=0){
                int result = matrix[pi][pj];
                res[pos] = result;
                pos++;
                pj--;
                if(pj<left){
                    pj++;
                    left++;
                    pi--;
                    break;
                }
            }
            if(pos>=total){
                break;
            }
            while (pi>=0){
                int result = matrix[pi][pj];
                res[pos] = result;
                pos++;
                pi--;
                if(pi<=top){
                    pi++;
                    top++;
                    pj++;
                    break;
                }
            }
        }
        return res;
    }

    public static void main(String[] args) {
        int a[][]={{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16}};
        int b[][]={{1,2,3},{4,5,6,},{7,8,9}};
        int c[][]={{1,2,3,4},{5,6,7,8},{9,10,11,12}};
        int d[][]={{1}};
        int[]res = spiralOrder(d);
        for (int i =0;i<res.length;i++){
            System.out.println(res[i]);
        }
    }
}