Adding Next_Greater_Element.cpp to cpp

cpp/Next_Greater_Element.cpp

@@ -0,0 +1,60 @@
+/*Problem Statement - Given an array, print the Next Greater Element (NGE) for every element. 
+The Next greater Element for an element x is the first greater element on the right side of x in the array. 
+Elements for which no greater element exist, consider the next greater element as -1. */
+
+//Problem Link - https://www.geeksforgeeks.org/next-greater-element/
+
+#include<bits/stdc++.h>
+using namespace std;
+vector<int> nextLargerElement(vector<int> arr, int n)
+{
+
+        vector<int> ans(n);
+        stack<int> st;
+        st.push(n-1);
+        ans[n-1]=-1;
+
+        for(int i=n-2; i>=0; i--)
+        {
+            if(st.empty())
+            {
+                ans[i] = -1;
+                st.push(i);
+            }
+            else
+            {
+                while(!st.empty() && arr[st.top()]<arr[i])
+                {
+                    st.pop();
+                }
+                if(st.empty())
+                {
+                    ans[i]=-1;
+                }
+                else
+                {
+                    ans[i] = arr[st.top()];
+                }
+                st.push(i);
+            }
+        }
+        return ans;
+}
+int main()
+{
+    int n;
+    cin>>n;
+
+    vector<int> arr(n);
+    for(int i=0; i<n; i++)
+    {
+        cin>>arr[i];
+    }
+
+    vector<int> ans = nextLargerElement(arr, n);
+    for(int i=0; i<n; i++)
+    {
+        cout<<ans[i]<<" ";
+    }
+    cout<<endl;
+}