LeetCode -- Spiral Matrix II

LeetCode -- Spiral Matrix II

題目描述：


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 ]
]


給定一個數字，由外到內生成矩陣。


思路：


本題主要是完成一個旋轉的過程，遍歷時track圈(cycle)的寬度，分為從左到右，上到下，右到左，左到上四個不同方向。每次cycle遞減。
其次要注意n為奇偶數的cycle值的不同。




實現代碼：

public class Solution {
    public int[,] GenerateMatrix(int n) {
        var matrix = new int[n,n];
	
    	var row = n % 2 == 0 ? n / 2 : (n+1) / 2;
    	var count = 1;
    	for(var cycle = 0;cycle < row; cycle++){
    		
    		// left to right
    		for(var col = cycle;col < n - cycle - 1; col++){
    			matrix[cycle,col] = count ++;
    		}
    		
    		// right to bottom
    		for(var r = cycle ; r < n - cycle; r++){
    			matrix[r, n - cycle - 1] = count ++;
    		}
    		
    		// bottom to left
    		for(var col = n - cycle - 2;col >= cycle; col --){
    			matrix[n-cycle-1,col] = count ++;
    		}
    		
    		// left to top
    		for(var r = n - cycle - 2;r > cycle; r --){
    			matrix[r,cycle] = count ++;
    		}
    	}
    	
    	return matrix;
    }
}