Print all numbers between 1 to N without using any loop

Write a program to print all numbers between 1 and N without using a loop.

Method 1: Using static variable in recursive main

The idea is to call the main() function recursively, and with each call, print the next element from the series. To store information about the previous element printed, we use a static variable (Note that a global variable will also work fine).

The following C++ program demonstrates it:

#include <iostream>

using namespace std;

#define N 100

int main()

{

static int i = 1;

if (i <= N && cout << i++ << " ") {

main();

}

return 0;

}

#include <iostream>

using namespace std;

#define N 100

int main()

{

static int i = 0;

if (i++ < N)

{

cout << i << " ";

main();

}

return 0;

}

Method 2: Using Recursion by implementing a separate method

#include <iostream>

using namespace std;

#define N 100

void print(int n)

{

if (n <= 0) {

return;

}

print(n - 1);

cout << n << " ";

}

int main()

{

print(N);

return 0;

}

#include <iostream>

using namespace std;

#define N 100

// Short–circuiting (not a conditional statement)

void print(int n) {

n && (print(n - 1), cout << n << " ");

}

int main()

{

print(N);

return 0;

}

Method 3: Using a MACRO

#include <iostream>

using namespace std;

#define COUT(i) cout << i++ << " ";

#define LEVEL(N) N N N N N N N N N N

#define PRINT(i) LEVEL(LEVEL(COUT(i))); // 100 = 10×10

int main()

{

int i = 1;

// prints numbers from 1 to 100

PRINT(i);

return 0;

}

Method 4: Without Recursion using struct/class with static field

#include <iostream>

using namespace std;

#define N 100

struct X

{

static int i;

X() {

cout << ++i << " ";

}

};

int X::i = 0;

int main()

{

X ob[N];

return 0;

}

We can also use the C++ class replacing struct.

#include <iostream>

using namespace std;

#define N 100

class X

{

static int i;

public:

X() {

cout << ++i << " ";

}

};

int X::i = 0;

int main()

{

X ob[N];

return 0;

}

Exercise: Extend method 3 to print numbers from 1 to 1000

References: https://stackoverflow.com/questions/4568645/printing-1-to-1000-without-loop-or-conditionals/

Print all numbers between 1 to N without using any loop | 4 methods

Method 1: Using static variable in recursive main

Method 2: Using Recursion by implementing a separate method

Method 3: Using a MACRO

Method 4: Without Recursion using struct/class with static field

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