Stack and Queues

Find the next Greater element

NextGreaterElement.cpp

@@ -0,0 +1,41 @@
+#include <bits/stdc++.h>
+using namespace std;
+//Time Complexity O(n)
+vector<long long> nextLargerElement(vector<long long> arr, int n){
+        vector<long long int>v;
+        stack<long long int>s;
+        for(int i=n-1;i>=0;i--)
+        {
+            if(s.size()==0)
+            v.push_back(-1);
+
+            else if(s.size()>0 && s.top()>arr[i])
+            v.push_back(s.top());
+
+            else 
+            {
+                while(s.size()>0 && s.top()<arr[i])
+                    s.pop();
+                if(s.size()==0)
+                v.push_back(-1);
+                else 
+                v.push_back(s.top());
+            }
+            s.push(arr[i]);
+        }
+        reverse(v.begin(),v.end());
+        return v;
+    }
+
+int main()
+{
+    int n;
+    cin>>n;
+    vector<long long int>a(n),res;
+    for(int i=0;i<n;i++)
+    cin>>a[i];
+    res=nextLargerElement(a,n);
+    for(int i=0;i<n;i++)
+    cout<<res[i]<<" ";
+    return 0;
+}