LeetCode: Spiral Matrix

题目：

顺时针打印矩阵

例子：

Example 1:
Input:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]
Output: [1,2,3,6,9,8,7,4,5]

Example 2:
Input:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

思路：

就是从左至右，从上至下，从右至左，从下至上进行打印矩阵即可，但是这里要注意只剩1行和1列的处理

代码:

class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList<>();
        if(matrix == null || matrix.length == 0){
            return result;
        }

        int rowBegin = 0;
        int rowEnd = matrix.length - 1;
        int colBegin = 0;
        int colEnd = matrix[0].length -1;

        while(rowBegin <= rowEnd && colBegin <= colEnd){
            for(int j = colBegin; j <= colEnd; j++){
                result.add(matrix[rowBegin][j]);
            }
            rowBegin ++;

            for(int i = rowBegin; i <= rowEnd ; i++){
                result.add(matrix[i][colEnd]);
            }
            colEnd -- ;

            if(rowBegin <= rowEnd){
                for(int j = colEnd ; j >= colBegin ;j-- ){
                    result.add(matrix[rowEnd][j]);
                }
            }
            rowEnd --;

            if(colBegin <= colEnd){
                for(int i = rowEnd ; i >= rowBegin; i--){
                    result.add(matrix[i][colBegin]);
                }
            }
            colBegin ++;
        }

        return result;

    }
}

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