g1101_1200.s1114_print_in_order.Foo Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of leetcode-in-java21 Show documentation

Java-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.38

package g1101_1200.s1114_print_in_order;

// #Easy #Concurrency #2023_06_01_Time_12_ms_(58.10%)_Space_41.7_MB_(65.01%)

/**
 * 1114 - Print in Order\.
 *
 * Easy
 *
 * Suppose we have a class:
 *
 * public class Foo { public void first() { print("first"); } public void second() { print("second"); } public void third() { print("third"); } }
 *
 * The same instance of `Foo` will be passed to three different threads. Thread A will call `first()`, thread B will call `second()`, and thread C will call `third()`. Design a mechanism and modify the program to ensure that `second()` is executed after `first()`, and `third()` is executed after `second()`.
 *
 * **Note:**
 *
 * We do not know how the threads will be scheduled in the operating system, even though the numbers in the input seem to imply the ordering. The input format you see is mainly to ensure our tests' comprehensiveness.
 *
 * **Example 1:**
 *
 * **Input:** nums = [1,2,3]
 *
 * **Output:** "firstsecondthird"
 *
 * **Explanation:** There are three threads being fired asynchronously. The input [1,2,3] means thread A calls first(), thread B calls second(), and thread C calls third(). "firstsecondthird" is the correct output.
 *
 * **Example 2:**
 *
 * **Input:** nums = [1,3,2]
 *
 * **Output:** "firstsecondthird"
 *
 * **Explanation:** The input [1,3,2] means thread A calls first(), thread B calls third(), and thread C calls second(). "firstsecondthird" is the correct output.
 *
 * **Constraints:**
 *
 * *   `nums` is a permutation of `[1, 2, 3]`.
**/
public class Foo {
    private volatile boolean firstFinished;
    private volatile boolean secondFinished;

    public void first(Runnable printFirst) {
        // printFirst.run() outputs "first". Do not change or remove this line.
        printFirst.run();
        firstFinished = true;
    }

    public void second(Runnable printSecond) {
        // printSecond.run() outputs "second". Do not change or remove this line.
        while (true) {
            if (firstFinished) {
                printSecond.run();
                secondFinished = true;
                break;
            }
        }
    }

    public void third(Runnable printThird) {
        // printThird.run() outputs "third". Do not change or remove this line.
        while (true) {
            if (firstFinished && secondFinished) {
                printThird.run();
                break;
            }
        }
    }
}