Spiral Matrix
Source
Given a matrix of m x n elements (m rows, n columns), return all elements of
the matrix in spiral order.
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].
Java
public class Solution {
public List<Integer> spiralOrder(int[][] matrix) {
List<Integer> result = new ArrayList<Integer>();
if(matrix==null || matrix.length==0 || matrix[0].length==0) return result;
int rowBegin = 0;
int rowEnd = matrix.length - 1;
int colBegin = 0;
int colEnd = matrix[0].length - 1;
while (true) {
for (int i = colBegin; i <= colEnd; ++i)
result.add(matrix[rowBegin][i]);
if (++rowBegin > rowEnd) break;
for (int i = rowBegin; i <= rowEnd; ++i)
result.add(matrix[i][colEnd]);
if (colBegin > --colEnd) break;
for (int i = colEnd; i >= colBegin; --i)
result.add(matrix[rowEnd][i]);
if (rowBegin > --rowEnd) break;
for (int i = rowEnd; i >= rowBegin; --i)
result.add(matrix[i][colBegin]);
if (++colBegin > colEnd) break;
}
return result;
}
}