374. Guess Number Higher or Lower
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 3 possible results:
-1: The number I picked is lower than your guess (i.e.pick < num).1: The number I picked is higher than your guess (i.e.pick > num).0: The number I picked is equal to your guess (i.e.pick == num).
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
Example 4:
Input: n = 2, pick = 2 Output: 2
Constraints:
1 <= n <= 231 - 11 <= pick <= n
Rust Solution
struct Solution;
static mut X: i32 = 0;
unsafe fn guess(num: i32) -> i32 {
use std::cmp::Ordering::*;
match X.cmp(&num) {
Equal => 0,
Greater => 1,
Less => -1,
}
}
impl Solution {
#[allow(non_snake_case)]
unsafe fn guessNumber(n: i32) -> i32 {
let mut l = 1;
let mut r = n;
while l < r {
let m = l + (r - l) / 2;
match guess(m) {
0 => {
return m;
}
-1 => {
r = m;
}
1 => {
l = m + 1;
}
_ => {}
}
}
l
}
}
#[test]
fn test() {
unsafe {
X = 6;
assert_eq!(Solution::guessNumber(10), 6);
}
}
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