Create ExponentialSearch

anahita-singla · abranhe · commit d53bc7e9e49c · 2020-10-06T16:48:38.000-04:00
diff --git a/searches/ExponentialSearch b/searches/ExponentialSearch
@@ -0,0 +1,66 @@
+// C++ program to find an element x in a 
+// sorted array using Exponential search. 
+#include <bits/stdc++.h> 
+using namespace std; 
+  
+int binarySearch(int arr[], int, int, int); 
+  
+// Returns position of first occurrence of 
+// x in array 
+int exponentialSearch(int arr[], int n, int x) 
+{ 
+    // If x is present at firt location itself 
+    if (arr[0] == x) 
+        return 0; 
+  
+    // Find range for binary search by 
+    // repeated doubling 
+    int i = 1; 
+    while (i < n && arr[i] <= x) 
+        i = i*2; 
+  
+    //  Call binary search for the found range. 
+    return binarySearch(arr, i/2, min(i, n), x); 
+} 
+  
+// A recursive binary search function. It returns 
+// location of x in  given array arr[l..r] is 
+// present, otherwise -1 
+int binarySearch(int arr[], int l, int r, int x) 
+{ 
+    if (r >= l) 
+    { 
+        int mid = l + (r - l)/2; 
+  
+        // If the element is present at the middle 
+        // itself 
+        if (arr[mid] == x) 
+            return mid; 
+  
+        // If element is smaller than mid, then it 
+        // can only be present n left subarray 
+        if (arr[mid] > x) 
+            return binarySearch(arr, l, mid-1, x); 
+  
+        // Else the element can only be present 
+        // in right subarray 
+        return binarySearch(arr, mid+1, r, x); 
+    } 
+  
+    // We reach here when element is not present 
+    // in array 
+    return -1; 
+} 
+  
+// Driver code 
+int main(void) 
+{ 
+   int arr[] = {2, 3, 4, 10, 40}; 
+   int n = sizeof(arr)/ sizeof(arr[0]); 
+   int x = 10; 
+   int result = exponentialSearch(arr, n, x); 
+   (result == -1)? printf("Element is not present in array") 
+                 : printf("Element is present at index %d", 
+                                                    result); 
+   return 0; 
+} 
