HASHMAP implementation

Author: dexterrxx31

Count_pair_sum_DSA_Problem_18_Array.cpp

@@ -0,0 +1,26 @@
+// https://practice.geeksforgeeks.org/problems/count-pairs-with-given-sum5022/1
+
+#include <bits/stdc++.h>
+#include <unordered_set>
+using namespace std;
+
+// int getPairsCount(int arr[], int n, int k)
+// {   
+//     int count = 0 ;
+//     for (int i = 0; i < n; i++)
+//     {
+//         int required_number = k - arr[i];
+        
+//     }
+//     return count ;
+// }
+
+int main()
+{
+    int arr[] = {1, 5, 7, 1};             // input array
+    int n = sizeof(arr) / sizeof(arr[0]); // size of an array
+    //int k = 6;                            // sum we need
+    cout<<mp[9] ;
+    //cout << getPairsCount(arr, n, k);
+    return 0;
+}

frequency_of_elements.cpp

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+#include <bits/stdc++.h>
+using namespace std;
+
+int main()
+{
+    int arr[] = {1, 2, 2, 2, 4, 1, 1, 7, 8, 7, 2, 9, 4, 4, 8, 8, 8, 8, 1};
+    int n = sizeof(arr) / sizeof(arr[0]);
+    unordered_map<int, int> freq;
+    for (int i = 0; i < n; i++)
+    {
+        freq[arr[i]]++;
+    }
+    // map  use Red Black tree n(logn)
+    // map<int,int>::iterator it ;
+    // unordered map takes hashing table n(1)
+    unordered_map<int, int>::iterator it;
+    for (it = freq.begin(); it != freq.end(); it++)
+    {
+        cout << it->first << "->" << it->second << endl;
+    }
+
+    return 0;
+}