## Algorithm

Problem Name: 1114. Print in Order

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]`.

## Code Examples

### #1 Code Example with C++ Programming

```Code - C++ Programming```

``````
class Foo {
public:
int count = 0;
mutex mtx;
condition_variable cv;
Foo() {
count = 1;
}

void first(function < void()> printFirst) {
unique_lock lck(mtx);
// printFirst() outputs "first". Do not change or remove this line.
printFirst();
count = 2;
cv.notify_all();
}

void second(function < void()> printSecond) {
unique_lock lck(mtx);
cv.wait(lck, [this]() { return count == 2;});
// printSecond() outputs "second". Do not change or remove this line.
printSecond();
count = 3;
cv.notify_all();
}

void third(function < void()> printThird) {
unique_lock lck(mtx);
cv.wait(lck, [this]() { return count == 3;});
// printThird() outputs "third". Do not change or remove this line.
printThird();
}
};
``````
Copy The Code &

Input

cmd
nums = [1,2,3]

Output

cmd
"firstsecondthird"

### #2 Code Example with Python Programming

```Code - Python Programming```

``````
class Foo(object):
def __init__(self):
self.two.acquire()
self.three.acquire()

def first(self, printFirst):
"""
:type printFirst: method
:rtype: void
"""
# printFirst() outputs "first". Do not change or remove this line.
printFirst()
self.two.release()

def second(self, printSecond):
"""
:type printSecond: method
:rtype: void
"""
self.two.acquire()
# printSecond() outputs "second". Do not change or remove this line.
printSecond()
self.three.release()

def third(self, printThird):
"""
:type printThird: method
:rtype: void
"""
self.three.acquire()
# printThird() outputs "third". Do not change or remove this line.
printThird()
``````
Copy The Code &

Input

cmd
nums = [1,2,3]

Output

cmd
"firstsecondthird"

### #3 Code Example with C# Programming

```Code - C# Programming```

``````
using System;

namespace LeetCode
{
public class Foo
{
private EventWaitHandle waitHandle1;
private EventWaitHandle waitHandle2;

public Foo()
{
waitHandle1 = new AutoResetEvent(false);
waitHandle2 = new AutoResetEvent(false);
}

public void First(Action printFirst)
{

// printFirst() outputs "first". Do not change or remove this line.
printFirst();

waitHandle1.Set();
}

public void Second(Action printSecond)
{
waitHandle1.WaitOne();

// printSecond() outputs "second". Do not change or remove this line.
printSecond();

waitHandle2.Set();
}

public void Third(Action printThird)
{
waitHandle2.WaitOne();

// printThird() outputs "third". Do not change or remove this line.
printThird();
}
}
}
``````
Copy The Code &

Input

cmd
nums = [1,3,2]

Output

cmd
"firstsecondthird"