Spiral Matrix
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].
Solution
按照题意输出即可
Complexity
时间复杂度 O(n),空间复杂度 O(1)
Code
public class Solution {
public List<Integer> spiralOrder(int[][] matrix) {
ArrayList<Integer> res = new ArrayList<Integer>();
if (matrix.length == 0 || matrix[0].length == 0) return res;
int n = matrix.length, m = matrix[0].length, row = 0, col = -1;
while (true) {
for (int i = 0; i < m; ++i) res.add(matrix[row][++col]);
if (--n == 0) break;
for (int i = 0; i < n; ++i) res.add(matrix[++row][col]);
if (--m == 0) break;
for (int i = 0; i < m; ++i) res.add(matrix[row][--col]);
if (--n == 0) break;
for (int i = 0; i < n; ++i) res.add(matrix[--row][col]);
if (--m == 0) break;
}
return res;
}
}