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LC_103_DesignCircularQueue.cpp
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LC_103_DesignCircularQueue.cpp
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#include <bits/stdc++.h>
using namespace std;
// Time Complexity: O(1)
// Space Complexity: O(N)
class MyCircularQueue
{
public:
MyCircularQueue(int k)
{
// the queue holding the elements for the circular queue
q.resize(k);
// the number of elements in the circular queue
cnt = 0;
// queue size
sz = k;
// the idx of the head element
headIdx = 0;
}
bool enQueue(int value)
{
// handle full case
if (isFull())
return false;
// Given an array of size of 4, we can find the position to be inserted using the formula
// targetIdx = (headIdx + cnt) % sz
// e.g. [1, 2, 3, _]
// headIdx = 0, cnt = 3, sz = 4, targetIdx = (0 + 3) % 4 = 3
// e.g. [_, 2, 3, 4]
// headIdx = 1, cnt = 3, sz = 4, targetIdx = (1 + 3) % 4 = 0
q[(headIdx + cnt) % sz] = value;
// increase the number of elements by 1
cnt += 1;
return true;
}
bool deQueue()
{
// handle empty case
if (isEmpty())
return false;
// update the head index
headIdx = (headIdx + 1) % sz;
// decrease the number of elements by 1
cnt -= 1;
return true;
}
int Front()
{
// handle empty queue case
if (isEmpty())
return -1;
// return the head element
return q[headIdx];
}
int Rear()
{
// handle empty queue case
if (isEmpty())
return -1;
// Given an array of size of 4, we can find the tailIdx using the formula
// tailIdx = (headIdx + cnt - 1) % sz
// e.g. [0 1 2] 3
// headIdx = 0, cnt = 3, sz = 4, tailIdx = (0 + 3 - 1) % 4 = 2
// e.g. 0 [1 2 3]
// headIdx = 1, cnt = 3, sz = 4, tailIdx = (1 + 3 - 1) % 4 = 3
// e.g. 0] 1 [2 3
// headIdx = 2, cnt = 3, sz = 4, tailIdx = (2 + 3 - 1) % 4 = 0
return q[(headIdx + cnt - 1) % sz];
}
bool isEmpty()
{
// no element in the queue
return cnt == 0;
}
bool isFull()
{
// return true if the count is equal to the queue size
// else return false
return cnt == sz;
}
private:
int cnt, sz, headIdx;
vector<int> q;
};
int main()
{
MyCircularQueue *obj = new MyCircularQueue(3);
cout << obj->enQueue(1) << endl;
cout << obj->enQueue(2) << endl;
cout << obj->enQueue(3) << endl;
cout << obj->enQueue(4) << endl;
cout << obj->Rear() << endl;
cout << obj->isFull() << endl;
cout << obj->deQueue() << endl;
cout << obj->enQueue(4) << endl;
cout << obj->Rear() << endl;
return 0;
}