374 Guess Number Higher or Lower - Easy

Problem:

We are playing the Guess Game. The game is as follows:

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I will tell you whether the number I picked is higher or lower than your guess.

You call a pre-defined API int guess(int num), which returns three possible results:

-1: Your guess is higher than the number I picked (i.e. num > pick).
1: Your guess is lower than the number I picked (i.e. num < pick).
0: your guess is equal to the number I picked (i.e. num == pick).

Return the number that I picked.

Example 1:

Input: n = 10, pick = 6 Output: 6

Example 2:

Input: n = 1, pick = 1 Output: 1

Example 3:

Input: n = 2, pick = 1 Output: 1

Constraints:

1 <= n <= 231 - 1
1 <= pick <= n

Problem Analysis:

perform binary search
Time Complexity: O(LogN)
Space Complexity: O(1)

Solutions:

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

class Solution:
    def guessNumber(self, n: int) -> int:
        l, r = 1, n

        while l <= r:
            m = (l+r)// 2
            res = guess(m)

            if res > 0:
                l = m + 1
            elif res < 0:
                r = m - 1
            else:
                # found 
                return m

Walter Teng.

374 Guess Number Higher or Lower - Easy

Problem:

Problem Analysis:

Solutions:

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