Suppose you are given the following code:
class FooBar {
public void foo() {
for (int i = 0; i < n; i++) {
print("foo");
}
}
public void bar() {
for (int i = 0; i < n; i++) {
print("bar");
}
}
}
The same instance of FooBar will be passed to two different threads. Thread A will call foo() while thread B will call bar(). Modify the given program to output “foobar” n times.
Example 1:
Input: n = 1 Output: "foobar" Explanation: There are two threads being fired asynchronously. One of them calls foo(), while the other calls bar(). "foobar" is being output 1 time.
Example 2:
Input: n = 2 Output: "foobarfoobar" Explanation: "foobar" is being output 2 times.
Solution: Mutex
C++
|
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class FooBar { private: int n; std::mutex m1_; std::mutex m2_; public: FooBar(int n) { this->n = n; m2_.lock(); } void foo(function<void()> printFoo) { for (int i = 0; i < n; i++) { m1_.lock(); // printFoo() outputs "foo". Do not change or remove this line. printFoo(); m2_.unlock(); } } void bar(function<void()> printBar) { for (int i = 0; i < n; i++) { m2_.lock(); // printBar() outputs "bar". Do not change or remove this line. printBar(); m1_.unlock(); } } }; |
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