ArrangingCoins.java

package com.fishercoder.solutions;

/**
 * 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.*/
public class ArrangingCoins {

    public static int arrangeCoins(int n) {
        if(n < 2) return n;
        int row = 0, count = 0;
        long sum = 0;
        while(sum < n){
            row += 1;
            sum += row;
            count++;
        }
        if(sum == n) return count;
        return count-1;
    }

    public static void main(String...args){
        int n = 3;//should be 2
        System.out.println(arrangeCoins(n));
    }
}