leetcode 54 Spiral Matrix ----- java

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].

这道题就是说给定一个数组，然后求一圈一圈的读取数字，然后返回，比较简单，就是注意边界条件就好了

 

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList<Integer>();
        if( matrix.length == 0)
            return result;
        int left = 0,right = matrix[0].length-1;
        int num = matrix.length>matrix[0].length?matrix[0].length:matrix.length;
        num = num%2 == 0?num/2:num/2+1;
        for(int circle = 0 ;circle<num;circle++){
            if( circle == matrix.length-circle-1){//只有一行
                for( int i = left;i<=right;i++)
                    result.add(matrix[circle][i]);
                return result;
            }
            if( left == right){//只有一列
                for( int i = circle;i<matrix.length-circle;i++)
                    result.add(matrix[i][right]);
                return result;
            }
            for( int i = left;i<=right;i++)
                result.add(matrix[circle][i]);
            for( int i = circle+1;i<matrix.length-circle;i++)
                result.add(matrix[i][right]);
            for( int i = right-1;i>=left;i--)
                result.add(matrix[matrix.length-circle-1][i]);
            for( int i = matrix.length-circle-2;i>circle;i--)
                result.add(matrix[i][left]);
            left++;
            right--;
        }
        return result;
    }
}