Merge pull request #469 from ajinkya-ch/TernarySearch

added ternary search algorithm

searching/ternarysearch.c

@@ -0,0 +1,83 @@
+ 
+#include <stdio.h> 
+  
+// Function to perform Ternary Search 
+int ternarySearch(int l, int r, int key, int ar[]) 
+{ 
+    if (r >= l) { 
+  
+        // Find the mid1 and mid2 
+        int mid1 = l + (r - l) / 3; 
+        int mid2 = r - (r - l) / 3; 
+  
+        // Check if key is present at any mid 
+        if (ar[mid1] == key) { 
+            return mid1; 
+        } 
+        if (ar[mid2] == key) { 
+            return mid2; 
+        } 
+  
+        // Since key is not present at mid, 
+        // check in which region it is present 
+        // then repeat the Search operation 
+        // in that region 
+  
+        if (key < ar[mid1]) { 
+  
+            // The key lies in between l and mid1 
+            return ternarySearch(l, mid1 - 1, key, ar); 
+        } 
+        else if (key > ar[mid2]) { 
+  
+            // The key lies in between mid2 and r 
+            return ternarySearch(mid2 + 1, r, key, ar); 
+        } 
+        else { 
+  
+            // The key lies in between mid1 and mid2 
+            return ternarySearch(mid1 + 1, mid2 - 1, key, ar); 
+        } 
+    } 
+  
+    // Key not found 
+    return -1; 
+} 
+  
+// Driver code 
+int main() 
+{ 
+    int l, r, p, key; 
+  
+    // Get the array 
+    // Sort the array if not sorted 
+    int ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 
+  
+    // Starting index 
+    l = 0; 
+  
+    // length of array 
+    r = 9; 
+  
+    // Checking for 5 
+  
+    // Key to be searched in the array 
+    key = 5; 
+  
+    // Search the key using ternarySearch 
+    p = ternarySearch(l, r, key, ar); 
+  
+    // Print the result 
+    printf("Index of %d is %d\n", key, p); 
+  
+    // Checking for 50 
+  
+    // Key to be searched in the array 
+    key = 50; 
+  
+    // Search the key using ternarySearch 
+    p = ternarySearch(l, r, key, ar); 
+  
+    // Print the result 
+    printf("Index of %d is %d", key, p); 
+}