Leetcode 441. Arranging Coins (Easy) (cpp)

Leetcode 441. Arranging Coins (Easy) (cpp)

Tag: Binary Search, Math

Difficulty: Easy

/*441. Arranging Coins (Easy)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 = 5The coins can form the following rows:¤¤ ¤¤ ¤Because the 3rd row is incomplete, we return 2.Example 2:n = 8The coins can form the following rows:¤¤ ¤¤ ¤ ¤¤ ¤Because the 4th row is incomplete, we return 3.*/class Solution {public:int arrangeCoins(int n) {if (n == 0) {return 0;}int l = 1, r = n;while (l < r) {long mid = l + (r - l + 1) / 2;if (mid * (mid + 1) / 2.0 <= n) {l = mid;}else if (mid * (mid + 1) / 2 > n) {r = mid - 1;}}return r;}};