Spiral Matrix

题目描述

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
For example,
Given the following matrix:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
You should return [1,2,3,6,9,8,7,4,5].

题目解答

解题思路

四个首尾指针jMin , jMax, iMin , iMax 来控制行列值的选取

代码实现

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
         if(matrix.length == 0 || matrix[0].length == 0)
            return new ArrayList<>();
        List<Integer> ret = new ArrayList<>();
        int iMin = 0, iMax = matrix.length - 1;
        int jMin = 0, jMax = matrix[0].length - 1;
        while(true){
            for(int j = jMin; j <= jMax; j++)
                ret.add(matrix[iMin][j]);
            if(++iMin > iMax)
                break;

            for(int i = iMin; i <= iMax; i++)
                ret.add(matrix[i][jMax]);
            if(jMin > --jMax)
                break;

            for(int j = jMax; j >= jMin; j--)
                ret.add(matrix[iMax][j]);
            if(iMin > --iMax)
                break;

            for(int i = iMax; i >= iMin; i--)
                ret.add(matrix[i][jMin]);
            if(++jMin > jMax)
                break;
        }
        return ret;
    }
}