leetcode: Add building h2o

leetcode/1117.building-h2o/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "lc-1117-building-h2o"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

leetcode/1117.building-h2o/src/main.rs

@@ -0,0 +1,106 @@
+// Copyright (c) 2023 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be
+// found in the LICENSE file.
+
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread;
+
+struct H2O {
+    water: String,
+    // true -> hydrogen
+    // false -> oxygen
+    mutex: Mutex<bool>,
+    cvar: Condvar,
+}
+
+fn print_atom(atom: char) {
+    print!("{atom}");
+}
+
+impl H2O {
+    const OXYGEN: char = 'O';
+    const HYDROGEN: char = 'H';
+    const RELEASE_HYDROGEN: bool = true;
+
+    pub fn new(water: &str) -> Self {
+        Self {
+            water: water.to_owned(),
+            mutex: Mutex::new(Self::RELEASE_HYDROGEN),
+            cvar: Condvar::new(),
+        }
+    }
+
+    pub fn oxygen(&self) {
+        let mut index = 0;
+        loop {
+            let mut mutex = self.mutex.lock().unwrap();
+            while *mutex == Self::RELEASE_HYDROGEN {
+                mutex = self.cvar.wait(mutex).unwrap();
+            }
+
+            let mut count = 0;
+            while index < self.water.len() && count < 1 {
+                if self.water.chars().nth(index) == Some(Self::OXYGEN) {
+                    print_atom(Self::OXYGEN);
+                    count += 1;
+                }
+                index += 1;
+            }
+
+            if count == 0 {
+                return;
+            }
+            assert_eq!(count, 1);
+            *mutex = Self::RELEASE_HYDROGEN;
+            self.cvar.notify_all();
+        }
+    }
+
+    pub fn hydrogen(&self) {
+        let mut index = 0;
+        let len = self.water.len();
+        loop {
+            let mut mutex = self.mutex.lock().unwrap();
+            while *mutex != Self::RELEASE_HYDROGEN {
+                mutex = self.cvar.wait(mutex).unwrap();
+            }
+
+            let mut count = 0;
+            while index < len && count < 2 {
+                if self.water.chars().nth(index) == Some(Self::HYDROGEN) {
+                    print_atom(Self::HYDROGEN);
+                    count += 1;
+                }
+                index += 1;
+            }
+
+            if count == 0 {
+                *mutex = !Self::RELEASE_HYDROGEN;
+                self.cvar.notify_all();
+                return;
+            }
+            assert_eq!(count, 2);
+            *mutex = !Self::RELEASE_HYDROGEN;
+            self.cvar.notify_all();
+        }
+    }
+}
+
+fn main() {
+    let s = "HOH";
+    let s = "OOHHHH";
+    let h2o = Arc::new(H2O::new(s));
+    let a = {
+        let h2o = Arc::clone(&h2o);
+        thread::spawn(move || {
+            h2o.oxygen();
+        })
+    };
+    let b = {
+        thread::spawn(move || {
+            h2o.hydrogen();
+        })
+    };
+    let _ = a.join();
+    let _ = b.join();
+}