Longest Increasing Subsequence and Euler totient function

cpp_algos/Euler_totient_function.cpp

@@ -0,0 +1,17 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int phi(int n) {
+    int result = n;
+    for (int i = 2; i * i <= n; i++) {
+        if (n % i == 0) {
+            while (n % i == 0)
+                n /= i;
+            result -= result / i;
+        }
+    }
+    if (n > 1)
+        result -= result / n;
+    return result;
+}
+

cpp_algos/Longest Increasing Subsequence.cpp

@@ -0,0 +1,67 @@
+/* A Naive C++ recursive implementation
+of LIS problem */
+#include <iostream>
+using namespace std;
+
+/* To make use of recursive calls, this
+function must return two things:
+1) Length of LIS ending with element arr[n-1].
+	We use max_ending_here for this purpose
+2) Overall maximum as the LIS may end with
+	an element before arr[n-1] max_ref is
+	used this purpose.
+The value of LIS of full array of size n
+is stored in *max_ref which is our final result
+*/
+int _lis(int arr[], int n, int* max_ref)
+{
+	/* Base case */
+	if (n == 1)
+		return 1;
+
+	// 'max_ending_here' is length of LIS
+	// ending with arr[n-1]
+	int res, max_ending_here = 1;
+
+	/* Recursively get all LIS ending with arr[0],
+	arr[1] ... arr[n-2]. If arr[i-1] is smaller
+	than arr[n-1], and max ending with arr[n-1]
+	needs to be updated, then update it */
+	for (int i = 1; i < n; i++) {
+		res = _lis(arr, i, max_ref);
+		if (arr[i - 1] < arr[n - 1]
+			&& res + 1 > max_ending_here)
+			max_ending_here = res + 1;
+	}
+
+	// Compare max_ending_here with the overall
+	// max. And update the overall max if needed
+	if (*max_ref < max_ending_here)
+		*max_ref = max_ending_here;
+
+	// Return length of LIS ending with arr[n-1]
+	return max_ending_here;
+}
+
+// The wrapper function for _lis()
+int lis(int arr[], int n)
+{
+	// The max variable holds the result
+	int max = 1;
+
+	// The function _lis() stores its result in max
+	_lis(arr, n, &max);
+
+	// returns max
+	return max;
+}
+
+/* Driver program to test above function */
+int main()
+{
+	int arr[] = { 10, 22, 9, 33, 21, 50, 41, 60 };
+	int n = sizeof(arr) / sizeof(arr[0]);
+	cout <<"Length of lis is "<< lis(arr, n);
+	return 0;
+}
+// This code is contributed by shivanisinghss2110