Java实现 LeetCode 54 螺旋矩阵

54. 螺旋矩阵

给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。

示例 1:

输入:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
输出: [1,2,3,6,9,8,7,4,5]
示例 2:

输入:
[
[1, 2, 3, 4],
[5, 6, 7, 8],
[9,10,11,12]
]
输出: [1,2,3,4,8,12,11,10,9,5,6,7]

class Solution {
    public List spiralOrder(int[][] matrix) {
        List result = new LinkedList<>();
        if(matrix.length==0)    return result;
        int upBound = 0;
        int rightBound = matrix[0].length-1;
        int leftBound = 0;
        int downBound = matrix.length-1;
        while(true){
            for(int i=leftBound; i<=rightBound; ++i)    
                result.add(matrix[upBound][i]);
            if(++upBound>downBound) break;
            for(int i=upBound; i<=downBound; ++i)   
                result.add(matrix[i][rightBound]);
            if(--rightBound=leftBound; --i)   
                result.add(matrix[downBound][i]);
            if(--downBound=upBound; --i)   
                result.add(matrix[i][leftBound]);
            if(++leftBound>rightBound)  break;
        }
        return result;
    }
}