arrangingCoins

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You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins.

Given n, find the total number of full staircase rows that can be formed.

n is a non-negative integer and fits within the range of a 32-bit signed integer.

Example 1:

n = 5

The coins can form the following rows:
¤
¤ ¤
¤ ¤

Because the 3rd row is incomplete, we return 2.
Example 2:

n = 8

The coins can form the following rows:
¤
¤ ¤
¤ ¤ ¤
¤ ¤

Because the 4th row is incomplete, we return 3.
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class Solution {
public:
	int arrangeCoins(int n) {
		long long sum = 0;
		int count = 0;
		while(sum<n){
			count++;
			sum = sum + count;
			
		
			}                         //需要注意int范围
		
		if (sum == n) {
			return count;
		}
		
		if (sum > n) {
			return count - 1;
		}
		return 0;
	}
};