LeetCode 441. Arranging Coins

Description

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.

Code

class Solution {
public:
    int arrangeCoins(int n) {
        int i = 1;
        while (n - i >= 0)
            n -= i++;
        return i - 1;
    }
};

Appendix

• Link: https://leetcode.com/problems/arranging-coins/
• Run Time: 32ms