Description
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 (the number I picked stays the same throughout the game).
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 - 11 <= pick <= n
Solutions
Solution 1: Binary Search
We perform a binary search in the interval [1,..n], and find the first number that satisfies guess(x) <= 0, which is the answer.
The time complexity is O(log n), where n is the upper limit given in the problem. The space complexity is O(1).
PythonJavaC++GoTypeScriptRustC#
# The guess API is already defined for you.
# @param num, your guess
# @return -1 if num is higher 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))(code-box)
/**
* 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;
}
}(code-box)
/**
* 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);
*/
class Solution {
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;
}
};(code-box)
/**
* 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
}(code-box)
/**
* 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;
}(code-box)
/**
* 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;
}
}
}
}
}(code-box)
/**
* 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;
}
}(code-box)
