GGiven a positive integer n, generate a square matrix filled with elements from 1 to n^2 in spiral order.
Example
Input: 3
Output:
[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]
Thoughts
- 和LC54的解法是一样的，
- 只要能够按照 Spiral的方向遍历一遍 matrix，都可以解决问题
Code(JAVA)
public int[][] generateMatrix(int n) {
int [][] res = new int[n][n];
int rowStart = 0, rowEnd = n - 1;
int colStart = 0, colEnd = n - 1;
int i = 1;
while(rowStart <= rowEnd && colStart <= colEnd){
//left -> right
for(int j = colStart; j <= colEnd; j++){
res[rowStart][j] = i;
i ++;
}
rowStart ++;
//up -> down
for(int j = rowStart; j <= rowEnd; j++){
res[j][colEnd] = i;
i ++;
}
colEnd --;
//right -> left
for(int j = colEnd; j >= colStart; j --) {
res[rowEnd][j] = i;
i ++;
}
rowEnd --;
//down -> up
for(int j = rowEnd; j >= rowStart; j--) {
res[j][colStart] = i;
i ++;
}
colStart ++;
}
return res;
}
