[LeetCode]54. Spiral Matrix

https://leetcode.com/problems/spiral-matrix/?tab=Description

旋转遍历二维数组

数组可能是[[1,2]]这种case，所以要保证rowBeg <= rowEnd && colBeg <= colEnd

public class Solution {
public List<Integer> spiralOrder(int[][] matrix) {

List<Integer> res = new ArrayList<Integer>();

if (matrix.length == 0) {
return res;
}

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

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

// Traverse Down
for (int j = rowBegin; j <= rowEnd; j ++) {
res.add(matrix[j][colEnd]);
}
colEnd--;

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

if (colBegin <= colEnd) {
// Traver Up
for (int j = rowEnd; j >= rowBegin; j --) {
res.add(matrix[j][colBegin]);
}
}
colBegin ++;
}

return res;
}
}