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Design a Stack With Increment Operation in C++
Suppose we want to design a stack that supports the following operations.
CustomStack(int maxSize) This 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) This inserts x to the top of the stack if the stack hasn't reached the maxSize.
int pop() This deletes and returns the top of stack or -1 if the stack is empty.
void inc(int k, int val) This 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.
To solve this, we will follow these steps −
Define two arrays st and inc, and create one integer type data cap
in the initializer, set cap := N and set inc := a new array of size N + 10
For the push(x) method, if size of stack is not cap, then insert x into st.
The pop() operation will be like −
if st is empty, then return -1
otherwise
top of stack := top of stack + inc[top index of stack]
if stack has some element, then increase inc[size of st - 2] by inc[size of st – 1]
inc[size of s - 1] := 0
x := last element of st
return x
The inc() method will work as follows −
decrease k by 1
k := min of k and size of st – 1
if k < 0, then return
increase inc[k] by val.
Example (C++)
Let us see the following implementation to get a better understanding −
#include <bits/stdc++.h>
using namespace std;
class CustomStack {
public:
vector <int> st;
vector <int> inc;
int cap;
CustomStack(int N) {
cap = N;
inc = vector <int>(N + 10);
}
void push(int x) {
if(st.size() == cap) return;
st.push_back(x);
}
int pop() {
if(st.empty()) return -1;
else{
st.back() += inc[st.size() - 1];
if(st.size() - 1 > 0 ){
inc[st.size() - 2] += inc[st.size() - 1];
}
inc[st.size() - 1] = 0;
int x = st.back();
st.pop_back();
return x;
}
}
void increment(int k, int val) {
k--;
k = min(k, (int)st.size() - 1);
if(k < 0) return;
inc[k] += val;
}
};
main(){
CustomStack ob(3);
ob.push(1);
ob.push(2);
cout << ob.pop() << endl;
ob.push(2);
ob.push(3);
ob.push(4);
ob.increment(5, 100);
ob.increment(2, 100);
cout << ob.pop() << endl;
cout << ob.pop() << endl;
cout << ob.pop() << endl;
cout << ob.pop() << endl;
}Input
See the main() in the program
Output
2 103 202 201 -1
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