Added C++ solutions

Author: prasanta10

C++/14_Lucky_Numbers.cpp

@@ -0,0 +1,33 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+bool isValid(int i)
+{
+    bool check = true;
+    while (i > 0)
+    {
+        int rem = i % 10;
+        if (rem != 4 || rem != 7) //conditions to check for validity
+            check = false;
+        i = i / 10;
+    }
+    return check;
+}
+
+int main()
+{
+    int a, b;
+    cin >> a >> b;   //input from user
+    int cnt = 0;
+    for (int i = a; i <= b; i++)
+    {
+        if (isValid(i))      //checking validity for each number in range a to b
+        {
+            cnt++;
+            cout << i << " ";
+        }
+    }
+    if (cnt == 0)  //if no number is valid then print -1
+        cout << -1 << endl;
+    return 0;
+}

C++/15_Numbers_Histogram.cpp

@@ -0,0 +1,22 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main()
+{
+    char ch;
+    cin >> ch; //input character
+    int n;
+    cin >> n;
+    vector<int> v(n); 
+    for (int i = 0; i < n; i++)
+        cin >> v[i];   //input
+    for (auto i : v)             
+    {
+        for (int j = 0; j < i; j++)
+        {
+            cout << ch; //printing the character Xi times
+        }
+        cout << endl;
+    }
+    return 0;
+}

C++/26_Binary_Search.cpp

@@ -0,0 +1,39 @@
+#include <bits/stdc++.h>
+using namespace std;
+ 
+int main()
+{
+    int n, q;
+    cin >> n >> q;  //input from user
+    vector<int> v(n);
+    for (int i = 0; i < n; i++)
+        cin >> v[i];
+    sort(v.begin(), v.end()); //sorting the vector to apply binary search
+    while (q--)  
+    {
+        int target;
+        cin >> target;
+        bool check = false;
+        int start = 0, end = n - 1;
+        while (start <= end)  //running Binary Search for each query
+        {
+            int mid = start + (end - start) / 2;
+            if (v[mid] == target)
+            {
+                  check = true;
+                  break;
+            }
+            else if (v[mid] < target)
+            {
+                start = mid + 1;
+            }
+            else
+                end = mid - 1;
+        }
+        if (check)   //condition
+            cout << "found" << endl;
+        else
+            cout << "not found" << endl;
+    }
+    return 0;
+}

README.md

@@ -91,8 +91,8 @@ In the "Repository" you will find the topics and its problems.
 |11|[Primes from 1 to n](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/J) | [C++](./C++/37_Primes_from_1to_n.cpp)
 |12|[Divisors](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/K) | [C++](./C++/38_Divisors.cpp)
 |13|[GCD](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/L) | [C++](./C++/13_GCD.cpp)
-|14|[Lucky Numbers](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/M)
-|15|[Numbers Histogram](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/N)
+|14|[Lucky Numbers](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/M) | [C++](./C++/14_Lucky_Numbers.cpp)
+|15|[Numbers Histogram](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/N) | [C++](./C++/15_Numbers_Histogram.cpp)
 |16|[Pyramid](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/O) | [C++](./C++/42_Pyramid.cpp)
 |17|[Shape1](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/P) | [C++](./C++/43_Shape1.cpp)
 |18|[Digits](https://codeforces.com/group/MWSDmqGsZm/contest/219432/problem/Q)  | [C++](./C++/44_Digits.cpp)
@@ -135,7 +135,7 @@ In the "Repository" you will find the topics and its problems.
 |23|[Mirror Array](https://codeforces.com/group/MWSDmqGsZm/contest/219774/problem/W) | [C++](./C++/mirror.cpp)
 |24|[8 Neighbors](https://codeforces.com/group/MWSDmqGsZm/contest/219774/problem/X)| [C++](./C++/neighbours.cpp)
 |25|[Range sum query](https://codeforces.com/group/MWSDmqGsZm/contest/219774/problem/Y) | [C++](./C++/rangeSumQuery.cpp)
-|26|[Binary Search](https://codeforces.com/group/MWSDmqGsZm/contest/219774/problem/Z)
+|26|[Binary Search](https://codeforces.com/group/MWSDmqGsZm/contest/219774/problem/Z) | [C++](./C++/26_Binary_Search.cpp)
 
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