Added Range search problem in Binary Searching.

Author: Sahil

Searching/binary search/cpp/RangeSearch.cpp

@@ -0,0 +1,65 @@
+// Find the range of a particular element occuring in a given sorted array.
+// If the element doesn't exist, return 1.
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int findleft(const vector<int>& A, int B, int low, int high){
+    int res = -1;
+    while(low <= high){
+        int mid = low + (high - low)/2;
+        if(A[mid] == B){
+            res = mid;
+            high = mid-1;
+        }else if(A[mid] < B){
+            low = mid+1;
+        }else high = mid-1;
+    }
+    if(res == -1)
+        return res;
+    return low;
+}
+
+int findright(const vector<int>& A, int B, int low, int high){
+    int res = -1;
+    while(low <= high){
+        int mid = low + (high - low)/2;
+        if(A[mid] == B){
+            res = mid;
+            low = mid+1;
+        }else if(A[mid] > B){
+            high = mid-1;
+        }else low = mid+1;
+    }
+    if(res == -1)return -1;
+    return low-1;
+}
+
+int main(int argc, char const *argv[])
+{
+    std::vector<int> v({1,2,2,3,3,3,4,4,4,4,5,6,7,8,8,8,8,8});
+
+    cout << "The input vector is: " << endl;
+    for(auto i: v){
+        cout << i << " ";
+    }
+    cout << endl;
+
+    cout << "The first and last index of occurance of element '8' is : " << findleft(v, 8, 0, v.size()-1)
+                                                                         << "  " 
+                                                                         << findright(v, 8, 0, v.size()-1) 
+                                                                         << endl;
+
+    cout << "The first and last index of occurance of element '1' is : " << findleft(v, 1, 0, v.size()-1)
+                                                                         << "  " 
+                                                                         << findright(v, 1, 0, v.size()-1) 
+                                                                         << endl;
+
+    cout << "The first and last index of occurance of element '10' is : " << findleft(v, 10, 0, v.size()-1)
+                                                                         << "  " 
+                                                                         << findright(v, 10, 0, v.size()-1) 
+                                                                         << endl;
+
+    return 0;
+}