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LeetCode-54-Spiral-Matrix.java
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LeetCode-54-Spiral-Matrix.java
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/*
LeetCode: https://leetcode.com/problems/spiral-matrix/
LintCode: http://www.lintcode.com/problem/spiral-matrix/
JiuZhang: http://www.jiuzhang.com/solutions/spiral-matrix/
ProgramCreek: http://www.programcreek.com/2013/01/leetcode-spiral-matrix-java/
Analysis:
*/
public class Solution {
public List<Integer> spiralOrder(int[][] matrix) {
List<Integer> result = new ArrayList<Integer>();
if(matrix == null || matrix.length < 1) return result;
int m = matrix.length, n = matrix[0].length;
if (m == 1 && n == 1) {
result.add(matrix[0][0]);
return result;
}
int x = 0, y = 0; // the start point
while (m > 0 && n > 0) {
// Consider how m == 1,n == 1 are handled.
if (m == 1) {
for (int i = 0; i < n; i++) result.add(matrix[x][y++]);
return result;
}
if (n == 1) {
for (int i = 0; i < m; i++) result.add(matrix[x++][y]);
return result;
}
// Be careful: consider carefully why n - 1 and m - 1 here.
for (int i = 0; i < n - 1; i++) result.add(matrix[x][y++]);
for (int i = 0; i < m - 1; i++) result.add(matrix[x++][y]);
for (int i = 0; i < n - 1; i++) result.add(matrix[x][y--]);
for (int i = 0; i < m - 1; i++) result.add(matrix[x--][y]);
m -= 2;
n -= 2;
// finally x, y will come back to the original start point, so we need increment
x++;
y++;
}
return result;
}
}