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Question
Formatted question description: https://leetcode.ca/all/374.html
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 predefined 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 <= 2^{31}  1
1 <= pick <= n
Algorithm
Binary search.
Code

public class Guess_Number_Higher_or_Lower { public class Solution extends GuessGame { public int guessNumber(int n) { int low = 1; int high = n; while (low <= high) { int mid = low + (high  low) / 2; int res = guess(mid); if (res == 0) return mid; else if (res < 0) high = mid  1; else low = mid + 1; } return 1; } } } // stub class GuessGame { public int guess(int i) { return 0; } } ############ /** * Forward declaration of guess API. * @param num your guess * @return 1 if num is lower than the guess number * 1 if num is higher than the guess number * otherwise return 0 * int guess(int num); */ public class Solution extends GuessGame { public int guessNumber(int n) { int left = 1, right = n; while (left < right) { int mid = (left + right) >>> 1; if (guess(mid) <= 0) { right = mid; } else { left = mid + 1; } } return left; } }

// OJ: https://leetcode.com/problems/guessnumberhigherorlower/ // Time: O(logN) // Space: O(1) class Solution { public: int guessNumber(int n) { int L = 1, R = n; while (L <= R) { int M = L + (R  L) / 2, g = guess(M); if (g == 0) return M; if (g == 1) L = M + 1; else R = M  1; } return 1; } };

# 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: return bisect.bisect(range(1, n + 1), 0, key=lambda x: guess(x)) ############ # 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 """ l, r = 1, n while l < r: m = l + (r  l) / 2 g = guess(m) if g == 1: r = m  1 elif g == 1: l = m + 1 else: return m return l

/** * Forward declaration of guess API. * @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 * func guess(num int) int; */ func guessNumber(n int) int { return sort.Search(n, func(i int) bool { i++ return guess(i) <= 0 }) + 1 }

/** * Forward declaration of guess API. * @param {number} num your guess * @return 1 if num is lower than the guess number * 1 if num is higher than the guess number * otherwise return 0 * var guess = function(num) {} */ function guessNumber(n: number): number { let l = 1; let r = n; while (l < r) { const mid = (l + r) >>> 1; if (guess(mid) <= 0) { r = mid; } else { l = mid + 1; } } return l; }

/** * Forward declaration of guess API. * @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 * int guess(int num); */ public class Solution : GuessGame { public int GuessNumber(int n) { int left = 1, right = n; while (left < right) { int mid = left + ((right  left) >> 1); if (guess(mid) <= 0) { right = mid; } else { left = mid + 1; } } return left; } }

/** * Forward declaration of guess API. * @param num your guess * @return 1 if num is lower than the guess number * 1 if num is higher than the guess number * otherwise return 0 * unsafe fn guess(num: i32) > i32 {} */ impl Solution { unsafe fn guessNumber(n: i32) > i32 { let mut l = 1; let mut r = n; loop { let mid = l + (r  l) / 2; match guess(mid) { 1 => r = mid  1, 1 => l = mid + 1, _ => break mid, } } } }