标签：highlight lint range where integer find convert com public
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.
Math Problem: 1 + 2 +3....+x = (x+1)*x/2, now we know it equals to n
(x+1)*x/2 = n -> x2 + x = 2n -> 4x2 + 4x = 8n -> (2x+1)(2x+1) = 8n +1 -> x = (sqrt(8n+1) - 1)/2
need to convert int to long to calcuate the result, and convert it back to int as result
public class Solution {
public int arrangeCoins(int n) {
return (int)(Math.sqrt(8 * (long)n + 1) - 1)/2;
}
}
[Leetcode + Lintcode] 441. Arranging Coins
标签：highlight lint range where integer find convert com public
原文地址：http://www.cnblogs.com/dty0102/p/6065188.html
