Spiral-matrix-ii
題目描述
Given an integer n, generate a square matrix filled with elements from 1 to n 2 in spiral order.
For example,
Given n =3,
[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]
public class Solution {
public int[][] generateMatrix(int n) {
int[][] res = new int[n][n];
if (n < 1)
return res;
int index = 1, rowStart = 0, rowEnd = n - 1, colStart = 0, colEnd = n - 1;
while (index <= n * n) {
for (int i = colStart; i <= colEnd; i++) {
res[rowStart][i] = index++;
}
for (int i = rowStart + 1; i <= rowEnd; i++) {
res[i][colEnd] = index++;
}
for (int i = colEnd - 1; i >= colStart; i--) {
res[rowEnd][i] = index++;
}
for (int i = rowEnd - 1; i > rowStart; i--) {
res[i][colStart] = index++;
}
rowStart += 1;
rowEnd -= 1;
colStart += 1;
colEnd -= 1;
}
return res;
}
}