Merge pull request #330 from ishan-pf/ishan-pf

WaveSort Question is added to the Sorting Algorithms Folder

Author: smv1999

Sorting Algorithms/wavesort.cpp

@@ -0,0 +1,73 @@
+/*Given a sorted array arr[] of distinct integers. Sort the array into a wave-like array and return it
+In other words, arrange the elements into a sequence such that arr[1] >= arr[2] <= arr[3] >= arr[4] <= arr[5].....
+
+Example 1:
+
+Input:
+n = 5
+arr[] = {1,2,3,4,5}
+Output: 2 1 4 3 5
+Explanation: Array elements after 
+sorting it in wave form are 
+2 1 4 3 5.
+
+Example 2:
+
+Input:
+n = 6
+arr[] = {2,4,7,8,9,10}
+Output: 4 2 8 7 10 9
+Explanation: Array elements after 
+sorting it in wave form are 
+4 2 8 7 10 9.
+
+
+Expected Time Complexity: O(n).
+Expected Auxiliary Space: O(1).
+
+Constraints:
+1 ≤ n ≤ 106
+0 ≤ arr[i] ≤107  
+
+
+solution : */
+
+#include<iostream>
+using namespace std;
+ 
+// A utility method to swap two numbers.
+void swap(int *x, int *y)
+{
+    int temp = *x;
+    *x = *y;
+    *y = temp;
+}
+ 
+// This function sorts arr[0..n-1] in wave form, i.e., arr[0] >=
+// arr[1] <= arr[2] >= arr[3] <= arr[4] >= arr[5] ....
+void WaveSort(int arr[], int n)
+{
+    // Traverse all even elements
+    for (int i = 1; i < n; i+=2)
+    {
+        // If current even element is smaller than previous
+        if ( arr[i-1] < arr[i] )
+            swap(&arr[i], &arr[i-1]);
+ 
+        // If current even element is smaller than next
+        if (arr[i] > arr[i+1] && i<= n-2 )
+            swap(&arr[i], &arr[i + 1]);
+    }
+}
+ 
+
+int main()
+{
+    int arr[] = {10, 90, 49, 2, 1, 5, 23};
+    int n = sizeof(arr)/sizeof(arr[0]);
+    WaveSort(arr, n);
+    for (int i=0; i<n; i++)
+       cout << arr[i] << " ";
+    return 0;
+}
+