Practice Questions for Recursion | Set 5
Question 1
Predict the output of following program. What does the following fun() do in general?
C++
#include <iostream> using namespace std; int fun(int a, int b) { if (b == 0) return 0; if (b % 2 == 0) return fun(a + a, b/2); return fun(a + a, b/2) + a; } int main() { cout << fun(4, 3) ; return 0; } // This code is contributed by SHUBHAMSINGH10 |
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C
#include<stdio.h> int fun(int a, int b) { if (b == 0) return 0; if (b % 2 == 0) return fun(a+a, b/2); return fun(a+a, b/2) + a; } int main() { printf("%d", fun(4, 3)); getchar(); return 0; } |
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Java
/*package whatever //do not write package name here */ import java.io.*; class GFG { static int fun(int a, int b) { if (b == 0) return 0; if (b % 2 == 0) return fun(a + a, b/2); return fun(a + a, b/2) + a; } public static void main (String[] args) { System.out.println(fun(4, 3)); } } // This code is contributed by SHUBHAMSINGH10 |
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Python3
def fun(a, b): if (b == 0): return 0 if (b % 2 == 0): return fun(a + a, b//2) return fun(a + a, b//2) + a # Driver code print(fun(4, 3)) # This code is contributed by SHUBHAMSINGH10 |
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C#
using System; class GFG{ static int fun(int a, int b) { if (b == 0) return 0; if (b % 2 == 0) return fun(a + a, b/2); return fun(a + a, b/2) + a; } static public void Main () { Console.Write(fun(4, 3)); } } // This code is contributed by SHUBHAMSINGH10 |
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Output:
12
It calulates a*b (a multipied b).
Question 2
In question 1, if we replace + with * and replace return 0 with return 1, then what does the changed function do? Following is the changed function.
C++
#include <iostream> using namespace std; int fun(int a, int b) { if (b == 0) return 1; if (b % 2 == 0) return fun(a*a, b/2); return fun(a*a, b/2)*a; } int main() { cout << fun(4, 3) ; getchar(); return 0; } //This code is contributed by shubhamsingh10 |
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C
#include<stdio.h> int fun(int a, int b) { if (b == 0) return 1; if (b % 2 == 0) return fun(a*a, b/2); return fun(a*a, b/2)*a; } int main() { printf("%d", fun(4, 3)); getchar(); return 0; } |
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Java
import java.io.*; class GFG { static int fun(int a, int b) { if (b == 0) return 1; if (b % 2 == 0) return fun(a*a, b/2); return fun(a*a, b/2)*a; } public static void main (String[] args) { System.out.println(fun(4, 3)); } } //This code is contributed by shubhamsingh10 |
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Python3
def fun(a, b): if (b == 0): return 1 if (b % 2 == 0): return fun(a*a, b//2) return fun(a*a, b//2)*a # Driver code print(fun(4, 3)) # This code is contributed by shubhamsingh10 |
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C#
using System; public class GFG{ static int fun(int a, int b) { if (b == 0) return 1; if (b % 2 == 0) return fun(a*a, b/2); return fun(a*a, b/2)*a; } static public void Main () { Console.WriteLine(fun(4, 3)); } } // This code is contributed by shubhamsingh10 |
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Output:
64
It calculates a^b (a raised to power b).
Question 3
Predict the output of following program. What does the following fun() do in general?
C++
#include <iostream> using namespace std; int fun(int n) { if (n > 100) return n - 10; return fun(fun(n+11)); } int main() { cout << " " << fun(99) << " "; getchar(); return 0; } // This code is contributed by Shubhamsingh10 |
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C
#include<stdio.h> int fun(int n) { if (n > 100) return n - 10; return fun(fun(n+11)); } int main() { printf(" %d ", fun(99)); getchar(); return 0; } |
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Java
import java.io.*; class GFG { static int fun(int n) { if (n > 100) return n - 10; return fun(fun(n+11)); } public static void main (String[] args) { System.out.println(" " + fun(99) + " "); } } // This code is contributed by Shubhamsingh10 |
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Python3
def fun(n): if (n > 100): return n - 10 return fun(fun(n + 11)) # Driver code print(fun(99)) # This code is contributed by Shubhamsingh10 |
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C#
using System; class GFG{ static int fun(int n) { if (n > 100) return n - 10; return fun(fun(n + 11)); } // Driver code static public void Main () { Console.WriteLine(fun(99)); } } // This code is contributed by Shubhamsingh10 |
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Output:
91
fun(99) = fun(fun(110)) since 99 ? 100
= fun(100) since 110 > 100
= fun(fun(111)) since 100 ? 100
= fun(101) since 111 > 100
= 91 since 101 > 100
Returned value of fun() is 91 for all integer rguments n 101. This function is known as McCarthy 91 function.
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