441. Arranging Coins
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 Solution {
public int arrangeCoins(int n) {
int a=1;
for(int i=n;i>0;i--){
a=(int)Math.sqrt(i*2);
if(i*2%a==0&&i*2%(a+1)==0)
break;
}
return a;
}
}
上面的代码会超时，使用下面的代码:
public class Solution {
public int arrangeCoins(int n) {
return (int) Math.floor((-1 + Math.sqrt(1+8*(long)n))/2.0);//Math.floor（n）取小于等于n的最大整数返回double型
}
}