FilesExpand file tree

 master

/

ImplementQueueUsingStacks.cpp

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

65 lines (61 loc) · 1.74 KB

 master

/

ImplementQueueUsingStacks.cpp

Top

File metadata and controls

• Code
• Blame

65 lines (61 loc) · 1.74 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

/*Implement the following operations of a queue using stacks.

*

*push(x) -- Push element x to the back of queue.

*pop() -- Removes the element from in front of queue.

*peek() -- Get the front element.

*empty() -- Return whether the queue is empty.

*Notes:

*You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.

*Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.

*You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).

*/

class Queue {

public:

stack <int> s,s2;

// Push element x to the back of queue.

void push(int x) {

s.push(x);

}

// Removes the element from in front of queue.

void pop(void) {

if(s.size()==1)

s.pop();

else

{

while(s.size()>1)

{

s2.push(s.top());

s.pop();

}

s.pop();

while(s2.size()>0)

{

s.push(s2.top());

s2.pop();

}

}

}

// Get the front element.

int peek(void) {

if(s.size()==1)

return s.top();

while(s.size()>1)

{

s2.push(s.top());

s.pop();

}

int temp=s.top();

s2.push(s.top());

s.pop();

while(s2.size()>0)

{

s.push(s2.top());

s2.pop();

}

return temp;

}

// Return whether the queue is empty.

bool empty(void) {

return s.empty();

}

};