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.
A:
class FooBar {
private:
int n;
mutex m1;
mutex m2;
public:
FooBar(int n) {
this->n = n;
m1.unlock();
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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