Google Interview Question for Software Engineer / Developers


Country: United States
Interview Type: In-Person




Comment hidden because of low score. Click to expand.
2
of 2 vote

Need to use a producer consumer queuel.

- Create a threadsafe q=queue<string> that should contain File paths (relative or absolute)
- Create a Thread pool of n threads that monitors q
- Each thread's task is to dequeue and delete
- Main thread will do the following:
-- Enumerate all children of the Folder
-- If child is File, add to q
-- If child is Folder, recurse

Should do the trick

- Pranay August 18, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Need to use a producer consumer queuel.

- Create a threadsafe q=queue<string> that should contain File paths (relative or absolute)
- Create a Thread pool of n threads that monitors q
- Each thread's task is to dequeue and delete
- Main thread will do the following:
-- Enumerate all children of the Folder
-- If child is File, add to q
-- If child is Folder, recurse

Should do the trick

- Pranay August 18, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Need to use a producer consumer queuel.

- Create a threadsafe q=queue<string> that should contain File paths (relative or absolute)
- Create a Thread pool of n threads that monitors q
- Each thread's task is to dequeue and delete
- Main thread will do the following:
-- Enumerate all children of the Folder
-- If child is File, add to q
-- If child is Folder, recurse

Should do the trick

- P August 18, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Need to use a producer consumer queue.

- Create a threadsafe q=queue<string> that should contain File paths (relative or absolute)
- Create a Thread pool of n threads that monitors q
- Each thread's task is to dequeue and delete
- Main thread will do the following:
-- Enumerate all children of the Folder
-- If child is File, add to q
-- If child is Folder, recurse

Should do the trick

- Anonymous August 18, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Need to use a producer consumer queue.

- Create a threadsafe q=queue<string> that should contain File paths (relative or absolute)
- Create a Thread pool of n threads that monitors q
- Each thread's task is to dequeue and delete
- Main thread will do the following:
-- Enumerate all children of the Folder
-- If child is File, add to q
-- If child is Folder, recurse

Should do the trick

- pp12 August 19, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

public void removeForceFJ(String filePath) {
        long startTime = System.nanoTime();
        File file = new File(filePath);
        if (file.exists()) {
            ForkJoinPool forkJoinPool = new ForkJoinPool();
            forkJoinPool.invoke(new ForkJoinTask(file));
        }
        long endTime = System.nanoTime();
        System.out.printf("timeTaken = %d ns %n", (endTime - startTime));
    }


    private static class ForkJoinTask extends RecursiveAction {

        private File file;

        ForkJoinTask(File file) {
            this.file = file;
        }

        @Override
        protected void compute() {
            if (file.isDirectory()) {
                File[] children = file.listFiles();
                if (children != null && children.length > 0) {
                    List<ForkJoinTask> forkJoinTaskList = new ArrayList<ForkJoinTask>();
                    for (File child : children) {
                        forkJoinTaskList.add(new ForkJoinTask(child));
                    }
                    invokeAll(forkJoinTaskList);
                }
                file.delete();
            } else {
                file.delete();
            }
        }
    }

- vp August 24, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

public void removeForceFJ(String filePath) {
        long startTime = System.nanoTime();
        File file = new File(filePath);
        if (file.exists()) {
            ForkJoinPool forkJoinPool = new ForkJoinPool();
            forkJoinPool.invoke(new ForkJoinTask(file));
        }
        long endTime = System.nanoTime();
        System.out.printf("timeTaken = %d ns %n", (endTime - startTime));
    }


    private static class ForkJoinTask extends RecursiveAction {

        private File file;

        ForkJoinTask(File file) {
            this.file = file;
        }

        @Override
        protected void compute() {
            if (file.isDirectory()) {
                File[] children = file.listFiles();
                if (children != null && children.length > 0) {
                    List<ForkJoinTask> forkJoinTaskList = new ArrayList<ForkJoinTask>();
                    for (File child : children) {
                        forkJoinTaskList.add(new ForkJoinTask(child));
                    }
                    invokeAll(forkJoinTaskList);
                }
                file.delete();
            } else {
                file.delete();
            }
        }
    }

- vp August 24, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

#include <string>
#include <mutex>
#include <thread>
#include <iostream>
#include <dirent.h>
#include <vector>
#include <sys/types.h>
#include <unistd.h>

using namespace std;

vector<string> buf;
int produced_count = 0;
int consumed_count = 0;
condition_variable counts_cv;
mutex counts_mutex;
vector<thread> threads;
int idle_threads_count = 0;
bool stop = false;

void ProduceFile(string const item)
{
	unique_lock<mutex> lock(counts_mutex);
	while (produced_count - consumed_count == buf.size()) {
		counts_cv.wait(lock);
	}
	buf[produced_count++ % buf.size()] = item;
	counts_cv.notify_all();
	cerr << "produced: " << item << "\n";
}

void ConsumeFiles()
{
	while (true) {
		unique_lock<mutex> lock(counts_mutex);
		while (produced_count == consumed_count) {
			++idle_threads_count;
			counts_cv.notify_all();
			counts_cv.wait(lock);
			--idle_threads_count;
			if (stop) {
				return;
			}
		}
		string item = buf[consumed_count++ % buf.size()];
		counts_cv.notify_all();
		lock.unlock();
		cerr << "removing file: " << this_thread::get_id() << ": " << item << "\n";
	}
}

void RemoveEmptyDir(string const &dir)
{
	unique_lock<mutex> lock(counts_mutex);
	while (idle_threads_count != threads.size()) {
		counts_cv.wait(lock);
	}
	cerr << "removing dir: " << dir << "\n";
}

void Rm(string const &dir_name)
{
	DIR *dir, *dir2;
	struct dirent *ent;
	if ((dir = opendir(dir_name.c_str())) != NULL) {
		while (ent = readdir(dir)) {
			string item_name(ent->d_name);
			string item(dir_name + '/' + item_name); 
			if (item_name != "." &&
				item_name != "..")
			{
				if ((dir2 = opendir(item.c_str())) != NULL) {
					closedir(dir2);
					Rm(item);
				} else {
					ProduceFile(item);
				}
			}
		}
		closedir(dir);
		RemoveEmptyDir(dir_name);
	}
}

void RemoveDir(string const &dir_name)
{
	buf.resize(16); // must be true: (INT_MAX + 1) % buf.size() == 0

	for (int i = 0; i < 8; ++i) {
		threads.push_back(thread(ConsumeFiles));
	}

    Rm(dir_name);

	unique_lock<mutex> lock(counts_mutex);
	stop = true;
	lock.unlock();
	counts_cv.notify_all();
	for (int i = 0; i < threads.size(); ++i) {
		threads[i].join();
	}
}

int main(int argvc, char const **argv)
{
	RemoveDir("./tmp");
    return 0;
}

- Alex August 25, 2017 | Flag Reply


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