[LeetCode] 441. Arranging Coins

Problem

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.

Solution

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