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1 | 1 | packagecom.fishercoder.solutions; |
2 | 2 |
|
3 | 3 | importjava.util.Stack; |
4 | | -/**Implement the following operations of a queue using stacks. |
| 4 | +/** |
| 5 | + * 232. Implement Queue using Stacks |
| 6 | + * |
| 7 | + * Implement the following operations of a queue using stacks. |
5 | 8 |
|
6 | 9 | push(x) -- Push element x to the back of queue. |
7 | 10 | pop() -- Removes the element from in front of queue. |
8 | 11 | peek() -- Get the front element. |
9 | 12 | empty() -- Return whether the queue is empty. |
| 13 | +
|
10 | 14 | Notes: |
11 | 15 | 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. |
12 | 16 | 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. |
13 | | - You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).*/ |
| 17 | + You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue). |
| 18 | + */ |
14 | 19 | publicclass_232 { |
15 | 20 |
|
16 | | -classMyQueue { |
| 21 | +publicstaticclassSolution1 { |
| 22 | +classMyQueue { |
17 | 23 |
|
18 | | -Stack<Integer>input =newStack(); |
19 | | -Stack<Integer>output =newStack(); |
| 24 | +Stack<Integer>input =newStack(); |
| 25 | +Stack<Integer>output =newStack(); |
20 | 26 |
|
21 | | -// Push element x to the back of queue. |
22 | | -publicvoidpush(intx) { |
23 | | -input.push(x); |
24 | | - } |
| 27 | +// Push element x to the back of queue. |
| 28 | +publicvoidpush(intx) { |
| 29 | +input.push(x); |
| 30 | +} |
25 | 31 |
|
26 | | -// Removes the element from in front of queue. |
27 | | -publicintpop() { |
28 | | -peek(); |
29 | | -returnoutput.pop(); |
30 | | - } |
| 32 | +// Removes the element from in front of queue. |
| 33 | +publicintpop() { |
| 34 | +peek(); |
| 35 | +returnoutput.pop(); |
| 36 | +} |
31 | 37 |
|
32 | | -// Get the front element. |
33 | | -publicintpeek() { |
34 | | -if (output.isEmpty()) { |
35 | | -while (!input.isEmpty()) { |
36 | | -output.push(input.pop()); |
| 38 | +// Get the front element. |
| 39 | +publicintpeek() { |
| 40 | +if (output.isEmpty()) { |
| 41 | +while (!input.isEmpty()) { |
| 42 | +output.push(input.pop()); |
| 43 | + } |
37 | 44 | } |
| 45 | +returnoutput.peek(); |
38 | 46 | } |
39 | | -returnoutput.peek(); |
40 | | - } |
41 | 47 |
|
42 | | -// Return whether the queue is empty. |
43 | | -publicbooleanempty() { |
44 | | -returninput.isEmpty() &&output.isEmpty(); |
| 48 | +// Return whether the queue is empty. |
| 49 | +publicbooleanempty() { |
| 50 | +returninput.isEmpty() &&output.isEmpty(); |
| 51 | + } |
45 | 52 | } |
46 | 53 | } |
47 | 54 | } |
| 55 | + |