So, I've been trying to get two integers from the user and the program should return the value of the larger one. Here is my sample program:
#include<stdio.h>
int larger(int a, int b);
int main()
{
int num1, num2;
printf("Enter first number: ");
scanf("%d", &num1);
printf("Enter second number: ");
scanf("%d", &num2);
printf("\n%d is larger than the other", larger(num1, num2) );
}
int larger(int a, int b)
{
if (a>b)
{
printf("%d", a);
}
else if(b>a){
printf("%d", b);
}
}
But the problem here is that whenever I compile then run the program an integer value of 1 is placed beside the sentence "is larger than the other" ,while the largest integer (the integer that should be beside the 'is larger than the other') is placed above the integer 1.
SAMPLE OUTPUT:
Enter first number: 5
Enter second number: 3
5
1 is larger than the other
What should I do to place the larger value placed where it should be?
int larger(int a, int b)
Your function doesn't have a return statement . If you want largest value between two you need to return it from function . Like this -
int larger(int a, int b)
{
if (a>b)
{
//printf("%d", a); unnecessary as you print value in main
return a;
}
else if(b>a){
//printf("%d", b);
return b;
}
else
return a; //in this case take care of output message as both variables will be equal
}
larger needs to actually return the larger value: write return a;, and return b; in the appropriate places. And the output will look odd if you retain the printf calls in that function.
Currently your program behaviour is undefined as the return value is missing: the output is currently arbitrary.
You're also not dealing with all possibilities. What should happen if a and b are equal? You must return something on all control paths.
Your function isn't returning anything, you need to enable compiler warnings or alternatively, get a new compiler.
That being said, in case you aren't afraid of boolean logic, the function can simply be written as
static inline bool larger (int a, int b)
{
return a > b;
}
Naturally, you'll have to rewrite main() to check the result:
if(larger (x, y))
{
printf("x larger than y");
}
In int function larger(int a, int b) you should just compare and return the value rather than printing it.
#include<stdio.h>
int larger(int a, int b);
int main()
{
int num1, num2, largeOftheTwo= 0;
printf("Enter first number: ");
scanf("%d", &num1);
printf("Enter second number: ");
scanf("%d", &num2);
if(num1 != num2)
printf("\n%d is larger than the other", larger(num1, num2));
else
printf("\n%d is equal to %d", num1, num2);
return 0;
}
int larger(int a, int b)
{
if (a>b)
return a;
else
return b;
}
Related
Using a recurrence function ,find a program that computes the multiplication of two numbers using addition operator.
What I found is as follows:
/*C program to multiply two numbers using plus operator.*/
#include <stdio.h>
int main()
{
int a,b;
int mul,loop;
printf("Enter first number: ");
scanf("%d",&a);
printf("Enter second number: ");
scanf("%d",&b);
mul=0;
for(loop=1;loop<=b;loop++){
mul += a;
}
printf("Multiplication of %d and %d is: %d\n",a,b,mul);
return 0;
}
However I'm not sure if the it uses a recurrence function,can someone check that and if it does use a recursive function then show me how to do that?
This simple logic should work for you:
int multiply(int a, int b)
{
if(a < b)
return multiply(b, a); // swap
else if(b != 0)
return (a + multiply(a, b - 1)); // recursion
else
return 0;
}
I am trying to make a program that scans 3 ints and then passes them through a function that sort them by this way- the biggest number will be at 'num3', the second will be at 'num2' and the lowest one will be at 'num1' but for some reason the program crashes when it gets to the sort function.
#include <stdio.h>
#include <stdlib.h>
void swap(int* a, int* b);
void changer(int* num1, int* num2, int* num3);
int main()
{
int num1 = 0;
int num2 = 0;
int num3 = 0;
printf("Please enter your value for 'num1': ");
scanf("%d", &num1);
getchar();
printf("Please enter your value for 'num2': ");
scanf("%d", &num2);
getchar();
printf("Please enter your value for 'num3': ");
scanf("%d", &num3);
printf("\nYour nums before- \n");
printf("num1 == %d\n", num1);
printf("num2 == %d\n", num2);
printf("num3 == %d\n", num3);
changer(&num1, &num2, &num3);
printf("\nYour nums after- \n");
printf("num1 == %d\n", num1);
printf("num2 == %d\n", num2);
printf("num3 == %d\n", num3);
system("PAUSE");
return 0;
}
void changer(int* num1, int* num2, int* num3)
{
if (*num1 > *num3)
{
swap(*num3, *num1);
}
else if (*num1 > *num2)
{
swap(*num1, *num2);
}
if (*num2 > *num3)
{
swap(*num3, *num2);
}
}
void swap(int* a, int* b)
{
int temp = *a;
*a = *b;
*b = temp;
}
You should not dereference the pointers when you pass them to swap() since it takes int * and you would be passing int thus causing undefined behavior and in your case a crash. The compiler should warn about incompatible parameters.
Change every occurrence of
swap(*num1, *num2);
/* ^ ^ remove these */
with
swap(num1, num2);
swap(int*, int*) expects the integer pointer to be passed in, assume the value of num1 = 0 and num2 = 2 and when you pass these values to swap(), by dereferencing you are invoking like this swap(0, 2) or on 32 bit system
swap(0x00000000, 0x00000002)
Inside swap(int* a, int* b) you dereference the memory location 0x00000000 (not the memory pointed to by a) at the line,
int temp = *a;
and then you dereference 0x00000002 b at this line and trying to assign it to 0x00000000 (by dereferencing *a)
*a = *b;
You are generating
Memory access violation condition.
which is causing the crash. Summarizing, please do not ignore compiler warnings. Compiler raises warning on the line where you are making swap() calls.
'int *' differs in levels of indirection from 'int'
Both functions take integer pointers (i.e., memory addresses of integers) as arguments. So, the values of the arguments a, b, num1, num2, and num3 must ALWAYS be memory addresses of integers. In the function changer, values of the variables num1, num2, and num3 are ALREADY memory addresses. When you write *num1, value of *num1 is integer but not the memory address of an integer. So, you need to call the function swap as follows:
swap(num3, num1);
swap(num1, num2);
swap(num3, num2);
Is there any other way to return a value to main function using void functions. I don't want to use the following way because I want to ask user to enters some values in main function and then check if those values are correct in the void function.
#include <stdio.h>
void fun_1(int *num1, int *num2) {
printf("Enter both numbers: ");
scanf("%d", num1);
scanf("%d", num2);
}
int main(void) {
int num1, num2, total;
fun_1(&num1, &num2);
total = num1 + num2;
printf("%d \n", total);
}
In this code we ask user to enter values in void function, but I would like to ask user to enter values in main!
There is another way to make use of global variables, but as your program grows more complex, it will probably create more hassles for you then it is worth.
If you use global variables to store your inputs inside the sub-function, then you can directly access them in your main() function to get the values. You won't be needing a return from your sub-function.
Having said that, it would be better to change the function return type (maybe returning a struct containing the user-supplied values, if you more than one value to be returned) to match your requirements.
If you want to read the values in main but check them (ex. make sure both are positive) in another function, you can do this:
#include <stdio.h>
void check_numbers(int num1, int num2, int *valid) {
if ((num1 > 0) && (num2 > 0)) {
*valid = 1;
} else {
*valid = 0;
}
}
int main(void) {
int num1, num2, total, valid;
printf("Enter both numbers: ");
scanf("%d", num1);
scanf("%d", num2);
check_numbers(num1, num2, &valid);
if (valid) {
total = num1 + num2;
printf("%d \n", total);
} else {
printf("numbers are invalid\n);
}
}
I am learning recursion and i encountered a conceptual doubt while solving the problem of calculation of remainder when a positive integer is a is divided by a positive integer b.
My code is:
#include<stdio.h>
#include<stdlib.h>
int x;
int rem(int a,int b)
{
x=a;
if(x>=b)
{
x=x-b;
rem(x,b);
}
printf("%d\n",x);
return x;
}
int main()
{
int a,b;
printf("Enter a & b\n");
scanf("%d %d",&a,&b);
int y =rem(a,b);
printf("rem is :%d",y);
return 0;
}
Its working fine. I have learned that for every call a new set of formal parameters and local variables are created.
So i experimented it by printing x on return of every recursive call!
But it is printing 1 1 1 1. Why is the value of x corresponding to a particular call not printed. ?
Why only the last modified value printed?.. Is that because i declared 'x' as global?
In this case perhaps you need only to move your print up
int rem(int a,int b)
{
x=a;
printf("%d\n",x);
if(x>=b)
{
x=x-b;
rem(x,b);
}
return x;
}
But I think you should avoid the use of global variables in a recursive alrotithm. It could make the algorithm very difficult to reason about. Recursive functions are better to be 'pure functions'.
It is because while x >= b, rem() is repeatedly called before printf()s are called. Only after x < b will the printf()s are called as each call on rem() unwinds.
You might want to make x local to rem() to get the desired result.
Ignoring issues with checking the return value from scanf() and that the two entered values are both positive, etc, I think you can and should avoid x altogether. You could use:
#include <stdio.h>
static int rem(int a, int b)
{
if (a >= b)
a = rem(a-b, b);
printf("%d\n", a);
return a;
}
int main(void)
{
int a, b;
printf("Enter a & b\n");
scanf("%d %d", &a, &b);
int y = rem(a, b);
printf("rem(%d, %d) is: %d\n", a, b, y);
return 0;
}
This code captures the return value from rem() at each level of recursion. In this case, because the returned value doesn't change as the recursion unwinds, you could use the global variable x, but there is no need for it, and you should avoid global variables whenever you can.
#include<stdio.h>
#include<conio.h>
int fun(int,int);
int main()
{
int a,b;
printf("enter two numbers");
scanf("%d %d",&a,&b);
fun(a,b);
//printf("%d",fun(a,b));
}
int fun(int a,int b)
{
if(a<b)
printf("%d",a);
if(a>=b)
a=fun(a-b,b);
return a;
}
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Hi I have written a c program that reads in 2 values then swaps them and prints the new values except the second value keeps showing 0. For example it you enter 10 for 'a' and 8 tor 'b', then a will be 8 but b will be 0. Does anyone know the solution to fix this? Here is the code:
#include <stdio.h>
int getData()
{
int a, b;
printf("Enter first number: ");
scanf("%d", &a);
printf("Enter second number: ");
scanf("%d", &b);
return(a, b);
}
void swapValues(int a, int b)
{
printf("The value of a is: %d", b);
printf("\nThe value of b is: %d", a);
return;
}
int main()
{
int a, b = getData();
swapValues(a, b);
return(0);
}
return (a, b);
doesn't do what you think it does, it's a misapplication of the comma operator.
The expression op1, op2 evaluates both op1 and op2 but gives you the value of op2. So it's not passing back a couple of values (although some languages like Python can do this sort of thing).
Similarly,
int a, b = getData();
won't grab the mythical two values returned from getData(). Rather it will set a to an indeterminate value and set b based on the single value returned from the function.
I would be looking at something like this:
#include <stdio.h>
int getData (char *which) {
int val;
printf ("Enter value for %s: ", which);
scanf("%d", &val);
return val;
}
void swapValues (int a, int b) {
printf("The swapped value of a is: %d\n", b);
printf("The swapped value of b is: %d\n", a);
}
int main (void) {
int a = getData ("a");
int b = getData ("b");
swapValues(a, b);
return 0;
}
You should also keep in mind that, if you actually want to swap the variables a and b and have that reflected back to main(rather than just print them as if they've been swapped), you'll need to pass pointers to them and manipulate them via the pointers.
C is a pass-by-value language meaning that changes to function parameters aren't normally reflected back to the caller. That would go something like this:
void swapValues (int *pa, int *pb) {
int tmp = *pa;
*pa = *pb;
*pb = tmp;
}
:
swapValues (&a, &b);
// a and b are now swapped.
You have unnecessarily complicated the whole thing.For one, something like return(a,b) is absurd in C.Further, if you intend to swap, why are you passing b as argument for the printf() meant to print 'a' and passing a to the printf() of 'b'?Anyways,here's a modified code that keeps it simple and gets the job done.
#include <stdio.h>
void swapValues()
{
int a, b,tem;
printf("Enter first number: ");
scanf("%d", &a);
printf("\nEnter second number: ");
scanf("%d", &b);
tem=a;
a=b;
b=tem;
printf("\nThe value of a is: %d", a);
printf("\nThe value of b is: %d", b);
}
int main()
{
swapValues();
return(0);
}
First of all you can't return more than one value in C. The way around that is to return a struct or pass the values address.
void getData(int *a,int* b)
{
//int a, b;
printf("Enter first number: ");
scanf("%d", a); // look here you passed the address of a to scanf
// by doing that scanf can write to a
printf("Enter second number: ");
scanf("%d", b);
//return(a, b);
}
The old main:
int main()
{
int a, b = getData(); // b gets the return value from getData()
// but a is still uninitialized
//to call the new function you have to do the following
int a,b;
getData(&a,&b);
swapValues(a, b);
return(0);
}
You cannot return multiple values from a C function. I'm not even sure why the statement return(a, b) compiles.
If you want to return more than value from a function you should either put them into an array or a structure. I'm going to use a structure to demonstrate one way to do this correctly. There are many ways to do this, but this one modifies you code the least.
struct TwoNums{
int a;
int b;
};
TwoNums getData()
{
/* This creates a new struct of type struct TwoNums */
struct TwoNums nums;
printf("Enter first number: ");
scanf("%d", &(nums.a));
printf("Enter second number: ");
scanf("%d", &(nums.b));
return(a, b);
}
void swapValues(int a, int b)
{
printf("The value of a is: %d", b);
printf("\nThe value of b is: %d", a);
return;
}
int main()
{
/* Get the whole structure in one call */
struct TwoNums nums = getData();
/* Call the swap function using fields of the structure */
swapValues(nums.a, nums.b);
return 0;
}
The first:
getData() function is written incorrectly.
You can not return more than one parameter from the function in C. So you can to separate data reading, or use pointers as below:
void getData(int* a, int* b) {
printf("Enter first number: ");
scanf("%d", a);
printf("Enter second number: ");
scanf("%d", b);
}
In main()
int a, b;
getData(&a, &b);
The second:
swapValues(int a, int b) does not swap the data.
More correct:
void swapValues(int* a, int* b) {
int tmp = *a;
*a = *b;
*b = tmp;
}
without using temporary variable.
So try this code
#include <stdio.h>
int swape()
{
int a,b;
printf("Enter first number: ");
scanf("%d", &a);
printf("Enter second number: ");
scanf("%d", &b);
a=a+b;
b=a-b;
a=a-b;
printf("The value of a is: %d", a);
printf("\nThe value of b is: %d", b);
}
int main()
{
swape();
return(0);
}