LeetCode -- Permutation Sequence

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public class Solution {
    public string GetPermutation(int n, int k) 
    {
        var nums = new List<int>();
    	var total = 1;
    	for(var i = 1;i <= n; i++)
    	{
    		total *= i;
    		nums.Add(i);
    	}
    	
    	var ret = "";
    	k--;
    	while(n > 0)
    	{
    		// total represent as (n-1)!
    		total /= n;
    		
    		// take the nums[k / (n-1)!] element
    		var index = k / total;
    		
    		var x = nums[index];
    		ret += x;
    		nums.RemoveAt(index);
    		
    		// next k would be k%(n-1)!
    		k = k % total;
    		
    		n--;
    	}
    	
    	return ret;
    }
}

LeetCode -- Permutation Sequence

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原文地址：http://blog.csdn.net/lan_liang/article/details/49531109