arranging-coins

https://leetcode.com/problems/arranging-coins/

public class Solution {
public int arrangeCoins(int n) {
// n >= x*(x+1)/2; 2n >= x^2 + x; 8n+1 >= 4x^2 + 4x + 1 = (2x+1)^2
// (8n+1)^(1/2) = 2x+1; x = ((8n+1)^(1/2)-1)/2;
// 注意下面的n要转成long,不然可能溢出
return (int)(Math.sqrt(8*(long)n+1)-1)/2;
}
}
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