-
Notifications
You must be signed in to change notification settings - Fork 2
/
IncrementalStack.java
86 lines (76 loc) · 3.26 KB
/
IncrementalStack.java
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
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
package Leetcode;
import java.util.ArrayDeque;
import java.util.Deque;
/**
* @author kalpak
*
* Design a stack which supports the following operations.
*
* Implement the CustomStack class:
*
* CustomStack(int maxSize) Initializes the object with maxSize which is the maximum number of elements in the stack or do nothing if the stack reached the maxSize.
* void push(int x) Adds x to the top of the stack if the stack hasn't reached the maxSize.
* int pop() Pops and returns the top of stack or -1 if the stack is empty.
* void inc(int k, int val) Increments the bottom k elements of the stack by val. If there are less than k elements in the stack, just increment all the elements in the stack.
*
*
* Example 1:
*
* Input
* ["CustomStack","push","push","pop","push","push","push","increment","increment","pop","pop","pop","pop"]
* [[3],[1],[2],[],[2],[3],[4],[5,100],[2,100],[],[],[],[]]
* Output
* [null,null,null,2,null,null,null,null,null,103,202,201,-1]
* Explanation
* CustomStack customStack = new CustomStack(3); // Stack is Empty []
* customStack.push(1); // stack becomes [1]
* customStack.push(2); // stack becomes [1, 2]
* customStack.pop(); // return 2 --> Return top of the stack 2, stack becomes [1]
* customStack.push(2); // stack becomes [1, 2]
* customStack.push(3); // stack becomes [1, 2, 3]
* customStack.push(4); // stack still [1, 2, 3], Don't add another elements as size is 4
* customStack.increment(5, 100); // stack becomes [101, 102, 103]
* customStack.increment(2, 100); // stack becomes [201, 202, 103]
* customStack.pop(); // return 103 --> Return top of the stack 103, stack becomes [201, 202]
* customStack.pop(); // return 202 --> Return top of the stack 102, stack becomes [201]
* customStack.pop(); // return 201 --> Return top of the stack 101, stack becomes []
* customStack.pop(); // return -1 --> Stack is empty return -1.
*
*
* Constraints:
*
* 1 <= maxSize <= 1000
* 1 <= x <= 1000
* 1 <= k <= 1000
* 0 <= val <= 100
* At most 1000 calls will be made to each method of increment, push and pop each separately.
*/
public class IncrementalStack {
private int maxSize;
int[] incrementCache;
Deque<Integer> stack;
public IncrementalStack(int maxSize) {
this.maxSize = maxSize;
this.incrementCache = new int[this.maxSize];
this.stack = new ArrayDeque<>();
}
public void push(int x) {
if(stack.size() < maxSize)
stack.push(x);
}
public int pop() {
int index = stack.size() -1;
if(index < 0)
return -1;
if(index > 0)
incrementCache[index - 1] += incrementCache[index]; // Propagate the increment value
int result = stack.pop() + incrementCache[index]; // update the value of interest and return.
incrementCache[index] = 0;
return result;
}
public void increment(int k, int val) {
int index = Math.min(stack.size(), k) - 1;
if(index >= 0)
incrementCache[index] += val;
}
}