Spiral Matrix
Created: February 17, 2019 by [lek-tin]
Last updated: February 17, 2019
Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
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]
Solution:
class Solution {
public List<Integer> spiralOrder(int[][] matrix) {
if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
return new ArrayList<>();
}
List<Integer> res = new ArrayList<>();
int left = 0;
int right = matrix[0].length - 1;
int top = 0;
int bottom = matrix.length - 1;
String dir = ">";
int x = 0; // column
int y = 0; // row
while (true) {
if (left > right || top > bottom) {
break;
}
res.add(matrix[y][x]);
if (dir == ">") {
if (x == right) {
dir = "v";
top++;
y++;
} else {
x++;
}
} else if (dir == "v") {
if (y == bottom) {
dir = "<";
right--;
x--;
} else {
y++;
}
} else if(dir == "<") {
if (x == left) {
dir = "^";
y--;
bottom--;
} else {
x--;
}
} else if (dir == "^") {
if (y == top) {
dir = ">";
left++;
x++;
} else {
y--;
}
}
}
return res;
}
}