problem

​​441. Arranging Coins​​

solution1:

class Solution {
public:
    int arrangeCoins(int n) {
        long sum = 0; 
        int curLevel = 0;
        while(sum<=n)
        {
            curLevel += 1;
            sum += curLevel;
        }
        return (curLevel-1);
    }
};

solution2:

class Solution {
public:
    int arrangeCoins(int n) {
        return (int)((sqrt(8*(long)n+1)-1)*0.5);//数学求和公式求解x,注意参数类型是否越界.
    }
};

solution3:

class Solution {
public:
    int arrangeCoins(int n) {
        if(n<=1) return n;//err.
        int left = 0, right = n, mid = 0;
        while(left<right)
        {
            mid = left + (right-left)*0.5;
            if((long)mid*(mid+1)*0.5 <= n) left = mid+1;
            else right = mid;
        }
        return left-1;//err.
    }
};

参考

1. ​​Leetcode_441. Arranging Coins​​;

完