Find first unlocked mutex

asdf.cpp

#include <mutex>
#include <vector>
#include <iostream>
#include <algorithm>

using namespace std;

int main() {
  vector<mutex> mutexes(20);
  for(int i = 0; i < 10; ++i)
  	mutexes[i].lock();
  const auto result = find_if(mutexes.begin(), mutexes.end(), [&](auto & mtx) {
    bool acquired = mtx.try_lock();
    if(acquired)
      mtx.unlock();
    return acquired;
  });
  cout << (result - mutexes.begin()) << '\n';
}