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spiralMatrixII.java
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75 lines (43 loc) · 1.64 KB
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// Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.
// For example,
// Given n = 3,
// You should return the following matrix:
// [
// [ 1, 2, 3 ],
// [ 8, 9, 4 ],
// [ 7, 6, 5 ]
// ]
public class Solution {
public int[][] generateMatrix(int n) {
int[][] spiral = new int[n][n];
if(n == 0) return spiral;
int rowStart = 0;
int colStart = 0;
int rowEnd = n - 1;
int colEnd = n -1;
int number = 1;
while(rowStart <= rowEnd && colStart <= colEnd) {
for(int i = colStart; i <= colEnd; i++) {
spiral[rowStart][i] = number++;
}
rowStart++;
for(int i = rowStart; i <= rowEnd; i++) {
spiral[i][colEnd] = number++;
}
colEnd--;
for(int i = colEnd; i >= colStart; i--) {
if(rowStart <= rowEnd) {
spiral[rowEnd][i] = number++;
}
}
rowEnd--;
for(int i = rowEnd; i >= rowStart; i--) {
if(colStart <= colEnd) {
spiral[i][colStart] = number++;
}
}
colStart++;
}
return spiral;
}
}