Here is a solution for leetcode problem 374. But I think it's not always correct on multi thread testing and don't know how to make it right.
The reason is: On each test, we write RwLock and drop, then run the guess_number function, which call guess function, which read RwLock. In the middle of one test, the value in RwLock may be potentially changed by another test.
How to make a mutable global, that can be locked in current thread, then only functions in current thread can read write it. Or can i transfer a RwLock write into read atomatically, so there's is no gap for other thread to acquire it.
use std::sync::RwLock;
static TARGET: RwLock<i32> = RwLock::new(0);
fn guess(n: i32) -> i32 {
let t = TARGET.read().unwrap();
match n.cmp(&t) {
std::cmp::Ordering::Less => 1,
std::cmp::Ordering::Equal => 0,
std::cmp::Ordering::Greater => -1,
}
}
struct Solution;
impl Solution {
fn guess_number(n: i32) -> i32 {
let mut l = 1;
let mut r = n;
while l <= r {
let m = l + (r - l) / 2;
match guess(m) {
-1 => r = m - 1,
1 => l = m + 1,
_ => return m,
}
}
-1
}
}
#[cfg(test)]
mod test {
use super::*;
fn test(n: i32, pick: i32) {
let mut t = TARGET.write().unwrap();
*t = pick;
drop(t);
let out = Solution::guess_number(n);
assert_eq!(out, pick);
}
#[test]
fn test1() {
test(10, 6);
}
#[test]
fn test2() {
test(1, 1);
}
#[test]
fn test3() {
test(2, 1);
}
}
