#### clueless coding// TODO: be smarter

Cracking the Coding Interview Elements of Programming Interviews Programming Interviews Exposed # LeetCode 441. Arranging Coins: Java Solution

## Problem Statement

You have a grand total of n coins that you want to form into a staircase. Every k-th row must have exactly k coins to be “full”.

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

You can assume that n is a non-negative integer and also fits within the range of a 32-bit signed integer.

``````Function Signature (Java):
int arrangeCoins(int n)

Inputs:
n = 5

Outputs:
2

We can create rows like this:
¤
¤ ¤
¤ ¤
There are 2 full rows.

Inputs:
n = 8

Outputs:
3

We can create rows like this:
¤
¤ ¤
¤ ¤ ¤
¤ ¤
There are 3 full rows.
``````

## TL;DR Code Solution

``````public int arrangeCoins(int n) {

int start = 0;
int end = n;
int mid = 0;

while (start <= end) {
mid = (start + end) >>> 1;
if ((0.5 * mid * mid + 0.5 * mid ) <= n) {
start = mid + 1;
} else {
end = mid - 1;
}
}

return start - 1;

}

``````