leetcode 374 猜数字大小 leetcode 441

和昨天的一样，无非判断条件，依然二分就好！！！

# The guess API is already defined for you.
# @param num, your guess
# @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
# def guess(num):

class Solution(object):
    def guessNumber(self, n):
        """
        :type n: int
        :rtype: int
        """
        low, high = 1, n
        while low <= high:
            mid = (low + high) / 2
            ret = guess(mid)
            if ret == -1:
                high = mid - 1
            elif ret == 1:
                low = mid + 1
            else:
                return mid

leetcode 441 解法也是二分，就是条件太TMD乱了，数学功底也不差，就是懵...

class Solution(object):
    def arrangeCoins(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n == 0:
            return 0
        low, high = 1, n
        while low <= high:
            mid = (low + high) / 2
            coinsLow = (1 + mid) * mid / 2
            coinsHigh = (1 + mid + 1) * (mid + 1) / 2
            if coinsLow < n and coinsHigh > n or coinsLow == n:
                return mid
            elif coinsHigh <= n:
                low = mid + 1                 
            elif coinsLow > n:
                high = mid - 1