Create Next Greater Element in Array.cpp

Implementing_queue_using_one_and_two_stacks.cpp

@@ -0,0 +1,116 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// using 2 stacks
+
+class Queue{
+  public:
+  stack<int> st1,st2;
+   void enqueue(int data);
+   void dequeue();
+
+
+};
+
+void Queue::enqueue(int data)
+{
+   st1.push(data);
+   cout<<"Pushed: "<< st1.top()<<endl;
+}
+
+void Queue::dequeue()
+{
+    if(st1.empty())
+    {
+        cout<<"Underflow"<<endl;
+        return;
+    }
+    while(!st1.empty())
+    {
+      st2.push(st1.top());
+      st1.pop();
+    }
+
+    cout<<"Popped: "<< st2.top()<<endl;
+    st2.pop();
+    while(!st2.empty())
+    {
+      st1.push(st2.top());
+      st2.pop();
+    }
+
+}
+
+
+int main()
+{
+    Queue q;
+    q.enqueue(10);
+    q.enqueue(20);
+    q.enqueue(30);
+    q.enqueue(40);
+    q.dequeue();
+    q.dequeue();
+    q.dequeue();
+    q.dequeue();
+    q.dequeue();
+}
+
+
+// Using 1 stack only...
+
+class Queue{
+  public:
+  stack<int> st;
+   void enqueue(int data);
+   int dequeue();
+
+
+
+};
+
+
+void Queue::enqueue(int data)
+{
+  st.push(data);
+  cout<<data<<": pushed"<<endl;
+}
+
+int Queue::dequeue()
+{
+    if(st.empty())
+    {
+        cout<<"UnderFlow"<<endl;
+        return -1;
+    }
+
+    int top=st.top();
+    st.pop();
+
+    if(!st.empty())
+    {
+       int deque_ele=dequeue();
+       st.push(top);
+       return deque_ele; 
+    }
+
+    return top;
+
+
+
+}
+
+int main()
+{
+    Queue q;
+    q.enqueue(10);
+    q.enqueue(20);
+    q.enqueue(30);
+    q.enqueue(40);
+   cout<< q.dequeue()<<" :Popped"<<endl;
+   cout<< q.dequeue()<<" :Popped"<<endl;
+   cout<< q.dequeue()<<" :Popped"<<endl;
+   cout<< q.dequeue()<<" :Popped"<<endl;
+   cout<< q.dequeue()<<" :Popped"<<endl;
+
+}

Next Greater Element in Array.cpp

@@ -0,0 +1,76 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// NGE without Stack O(1)-> S.C.
+
+//Function to find the next greater element for each element of the array.
+vector<long long> nextLargerElement(vector<long long> nums, int n)
+{
+  // Your code here
+  vector<long long> result(n, -1);
+
+  long long max_element = nums[n - 1]; // initialize the maximum element as the last element
+
+  for (long long i = n - 2; i >= 0; i--)
+  {
+    if (nums[i] >= max_element)
+    {
+      max_element = nums[i]; // update the maximum element if the current element is greater
+    }
+    else
+    {
+      int j = i + 1;
+      while (j < n && nums[i] >= nums[j])
+      {
+        j++;
+      }
+      if (j < n && nums[i] < nums[j])
+      {
+        result[i] = nums[j]; // update the result vector with the next greater element
+      }
+    }
+  }
+  return result;
+}
+
+
+
+//    Returns the index of Next Greater element
+vector<int> n_g_e(vector<int> &nums)
+{
+  stack<int> st;
+  vector<int> ans;
+  ans.push_back(-1);
+  st.push(nums.size() - 1);
+  int n = nums.size();
+
+  for (int i = n - 2; i >= 0; i--)
+  {
+    //  iska matlab he ki muje next small chahiye tha pr muje grater milra h previous me, to hm pop() krdege...
+    while (!st.empty() && nums[i] >= nums[st.top()])
+    {
+      st.pop();
+    }
+
+    if (st.empty())
+    {
+      ans.push_back(-1);
+    }
+
+    else
+    {
+      ans.push_back(st.top());
+    }
+
+    st.push(i);
+  }
+
+  reverse(ans.begin(), ans.end());
+
+  for (int i = 0; i < ans.size(); i++)
+  {
+    cout << ans[i] << " ";
+  }
+
+  return ans;
+}