Recursion problem

[MrNoob]

Hey i m reading tutrial about rucursion and got code whish isnt complicated or anything but i dunno why it prints the way it does

/* recur.c -- recursion illustration */

#include <stdio.h>

void up_and_down(int);



int main(void)

{

    up_and_down(1);

    return 0;

}



void up_and_down(int n)

{

    printf("Level %d: n location %p\n", n, &n); /* 1 */

    if (n < 4)

         up_and_down(n+1);

    printf("LEVEL %d: n location %p\n", n, &n); /* 2 */



}

here it prints
Level 1: n location 0022FF60
Level 2: n location 0022FF40
Level 3: n location 0022FF20
Level 4: n location 0022FF00
LEVEL 4: n location 0022FF00
LEVEL 3: n location 0022FF20
LEVEL 2: n location 0022FF40
LEVEL 1: n location 0022FF60

first i know why it prints from 1 to 3 but see here it keeps calling itself till number is smaller than 4 right then after it finishes it goes back to that printf after that if statement whish should print the normal i whish is 1 but it doesnt it prints 4 4 3 2 1 why it got decremented there nowhere in the code where it said i-1 even when the function called itself even if we alrdy specified i as 1 and function calling itself somehow decremented it should when i==3 that if statement will terminate whish will print then orginal i ?

[Salem]

At the tip, you've got

up_and_down(1)
  up_and_down(2)
    up_and_down(3)
      up_and_down(4)

There is no subtraction, just a nested set of values stored as local parameter 'n'.
As you return from each recursive call, you get back the previous value of n.

[MrNoob]

oh so it keep calling function till ruc level 4 then it goes to other function whish level 3 then level 2 then level 1 again whish is the main one ?

[Salem]

Exactly.

[MrNoob]

oh thanks if only the book would put it in that simple

[ankush chander]

Hey i m reading tutrial about rucursion and got code whish isnt complicated or anything but i dunno why it prints the way it does

/* recur.c -- recursion illustration */

#include <stdio.h>

void up_and_down(int);



int main(void)

{

    up_and_down(1);

    return 0;

}



void up_and_down(int n)

{

    printf("Level %d: n location %p\n", n, &n); /* 1 */

    if (n < 4)

         up_and_down(n+1);

    printf("LEVEL %d: n location %p\n", n, &n); /* 2 */



}

here it prints
Level 1: n location 0022FF60
Level 2: n location 0022FF40
Level 3: n location 0022FF20
Level 4: n location 0022FF00
LEVEL 4: n location 0022FF00
LEVEL 3: n location 0022FF20
LEVEL 2: n location 0022FF40
LEVEL 1: n location 0022FF60

first i know why it prints from 1 to 3 but see here it keeps calling itself till number is smaller than 4 right then after it finishes it goes back to that printf after that if statement whish should print the normal i whish is 1 but it doesnt it prints 4 4 3 2 1 why it got decremented there nowhere in the code where it said i-1 even when the function called itself even if we alrdy specified i as 1 and function calling itself somehow decremented it should when i==3 that if statement will terminate whish will print then orginal i ?

reply:as the last printf stement s the part of the function up n down it will be executed as many times as the function is called,but before the statement is executed the function is called again and again untill n becomes4. now when the func is excuted for the last time it executes the last printf statement and returns to its calling function to execute it's last printf statement.hence the pattern 4 3 2 1.