Merge pull request matthewsamuel95#136 from sanchaymittal/patch-10

Randomized algorithms

Author: matthewsamuel95

Math/Randomized algorithms/ Random_Number_Selection_from_Array.cpp

@@ -0,0 +1,44 @@
+//Randomly select a number from a set of numbers.
+#include<bits/stdc++.h>
+
+using namespace std;
+
+int selectRandom(int x)
+{
+    static int res;    // The resultant random number
+    static int count = 0;  //Count of numbers visited so far in stream
+
+    count++;  // increment count of numbers seen so far
+
+    // If this is the first element from stream, return it
+    if (count == 1)
+        res = x;
+    else
+    {
+        // Generate a random number from 0 to count - 1
+        int i = rand() % count;
+
+        // Replace the prev random number with new number with 1/count probability
+        if (i == count - 1)
+            res  = x;
+    }
+    return res;
+}
+
+int main()
+{
+
+    int n;
+    cout<<"Enter the Number of elements to be inserted in Array : ";
+    cin >> n;
+
+    int a[n];
+
+    for (int i = 0; i < n; i++){
+      cin>>a[i];
+    }
+
+    for (int i = 0; i < n; ++i)
+        printf("Random number from first %d numbers is %d \n",i+1, selectRandom(a[i]));
+    return 0;
+}