Im learning from start C basic.And i dont understand character wide.When i change it nothing visual happens,so i dont know what is purpose of this
I was researching and at first i discovered that its not string length but
character datatype,but more info i wasnt able to find
main()
{
float farh, celsium ;
int lower, upper, step;
lower = 0;
upper = 300;
step = 20;
farh = lower;
while(farh <= upper) {
celsium = (5.0/9.0) * (farh - 32.0);
printf( "%5.2f %5.2f\n",farh, celsium);
farh = farh + step;
}
}
output is temperature in celsuim and fahrenheit (0.000000 -17.777779)
in the code above
%5.2f
represent each argument to be alerted with character wide at least 5 and with 2 numbers after decimal point. But what changes if i write 2, 6 or other number instead of 5?
printf("%5.2f\n", 3.223467856);
Consider the above statement:
printing with %5.2f will generate : _3.22 ( the symbol _ represents a blank space at the beginning, won't be printed in console)
5: The number will occupy space of 5 character wide. (.) dot occupies 1 char space too)
2: The number will occupy 2 digits after decimal point(.)
printf("%6.2f\n", 3.223467856);
printing with %6.2f will generate : __3.22
printf("%6.3f\n", 3.223467856);
printing with %6.2f will generate : _3.223
If you modify the program (with some cleanup):
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int const lower_limit = 0;
int const upper_limit = 300;
int const step = 20;
float fahrenheit = lower_limit;
while (fahrenheit <= upper_limit) {
float const celsius = (5.0f / 9.0f) * (fahrenheit - 32.0f);
printf("%9.6f\t%10.6f\n", fahrenheit, celsius);
fahrenheit += step;
}
return EXIT_SUCCESS;
}
You'll see the difference between %9.6f and %10.6f which should show something like:
0.000000 -17.777779
20.000000 -6.666667
40.000000 4.444445
60.000000 15.555556
80.000000 26.666668
100.000000 37.777779
120.000000 48.888893
140.000000 60.000004
160.000000 71.111115
180.000000 82.222229
200.000000 93.333336
220.000000 104.444450
240.000000 115.555557
260.000000 126.666672
280.000000 137.777786
300.000000 148.888901
You see a difference in behaviour when fahrenheit goes from 0 to 20 vs from 80 to 100.
Related
I'm trying to make a logarithm calculator and got stuck—it doesn't print out a value. The problem may be at lines 15 or 24 or both. How can I make it print the value (all written in C).
Here's the full code:
#include <stdio.h>
#include <stdlib.h>
// Finds base 10 logarithms
int main()
{
float result;
float base = 10.0;
float multiplier = 1.0;
// float counter1 = 0.0;
// float counter2 = 0;
printf("Input result: ");
scanf("%l", result);
// Solves for all results above the base
if(result > base) {
while(result > multiplier) {
multiplier = multiplier * multiplier; // the multiplier has to check non-whole numbers
multiplier += 0.001;
} // division
}
printf("Your exponent is: %l \n", &multiplier);
printf("Hello mathematics!");
return 0;
}
All help appreciated,
Xebiq
you should delete & in printf,and add & in scanf.
printf("Your exponent is: %f \n", multiplier);
scanf("%f", &result);
and use %f in them.
and with base 10 I suggest this function to calculate log:
unsigned int Log2n(unsigned int n)
{
return (n > 1) ? 1 + Log2n(n / 10) : 0;
}
also you should know about Floating-point numbers here:
multiplier += 0.001;
probably exactly 0.001 won't be added to multiplier when I debugged this 0.00100005 was being add to multiplier in my compiler.(which will affect multiplying)
In printf remove '&' and in scanf add '&' before variable.
Code simulates the rolling of two die 36000 times and outputs "Sum = _; Frequency = _; Percentage = _". Compiled code outputs everything correctly except percentage. "Percentage = 0" when it should output the quotient of "(frequency[calcCount] /36000) * 100" Is this a conflict in data type? How can I properly output the quotient?
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SUM_SIZE 36000
#define FREQUENCY_SIZE 13
int main(void){
int rollCount; // counter to loop through 36000 rolls of dice & sums
int calcCount; //counter to loop through frequencies 1-12 of sum calculation
//initialize frequency counters to 0
int frequency[FREQUENCY_SIZE] = {0};
//calculation array
int calculation[SUM_SIZE];
//seed
srand((unsigned)(time(NULL)));
for (rollCount = 1; rollCount <= SUM_SIZE; rollCount++){
//rolling first die
int face1 = (1 + ( rand() % 6));
//rolling second die
int face2 = (1 + ( rand() % 6));
int sum = face1 + face2;
//initializing array elements
calculation[rollCount] = sum;
//for each roll, select value of an element of array calculation
//and use that value as subscript in array frequency to determine
//element to increment (which in this case is the sum frequency)
++frequency[calculation[rollCount]];
}
//displaying results
for (calcCount = 2; calcCount < FREQUENCY_SIZE; calcCount++){
//calculating percentage
int percentage = (frequency[calcCount] /36000) * 100;
printf("Sum = %d; Frequency = %d; Percentage = %d \n", calcCount, frequency[calcCount], percentage);
}
}
When you do a division between two integers, the result will also be an integer and the "exact" result is truncated to fit an integer. Examples:
3/2 -> 1
10/3 -> 3
5/10 -> 0
and when you do
int percentage = (frequency[calcCount] /36000) * 100;
the part frequency[calcCount] /36000 is calculated first. It is a division between two int and it will give the result zero because frequency[calcCount] is less than 36000. Consequently multiplying with 100 still gives zero.
Instead do the multiplication first - like:
int percentage = (100 * frequency[calcCount]) /36000;
Another alternative is to use floating point like:
double percentage = (frequency[calcCount] /36000.0) * 100;
^^^
Notice the .0 to make 36000 a double
but then you need to change the print to use %f
double percentage = (frequency[calcCount] / 36000.0) * 100;
printf("Sum = %d; Frequency = %d; Percentage = %.2f \n", calcCount, frequency[calcCount], percentage);
^^^
Notice this to print the double
I'm basically trying to make a math rotation program in C. But the output is always wrong. P(x,y) is rotated about Q(r,s); clockwise (direction=1) or anticlockwise (direction=0). The a,b,c are angles in triple ,I guess question meant c is in hundred's then b is in ten's and a is unit's.
Input:
0
7 3
0 1 1
0 0
Output: -3 7
Whereas I'm getting -5 5.
Thanks for your time if you help me.
Original question link: https://www.codechef.com/problems/DSPC305
i found another question by the same uploader which uses TRIPLE too. He further added a note :Triple is defined by a,b,c where a is base, b is height and c is hypotenuse of a triangle. Each triple corresponds to an angle given by cosA= a/c
#include<stdio.h>
#include<math.h>
int main() {
int x,y,a,b,direction,c,r,s,xnew,ynew;
scanf("%i", &direction);
scanf("%i %i", &x, &y);
scanf("%i %i %i" , &a, &b, &c);
scanf("%i %i", &r, &s);
float PI = 3.1415926535897932384626;
float theta = ((c*100+b*10+a)*PI)/180;
if (direction==1)
{
xnew= (x-r) * cos(theta) + (y-s) * sin(theta);
ynew= -(x-r) * sin(theta) + (y-s) * cos(theta);
printf("%i %i", xnew+r, ynew+s);
}
if (direction==0)
{
xnew =( (x-r) * ((cos(theta))) - (y-s) * sin(theta));
ynew =( (x-r) * ((sin(theta))) + (y-s) * cos(theta));
printf("%i %i", (xnew+r), (ynew+s));
}
return 0;
}
This
float theta = ((c*100+b*10+a)*PI)/180;
has nothing to do with the definition of a triple.
You can use this code:
#include<stdio.h>
#include<math.h>
int main()
{
double xp,yp,xq,yq,a,b,c;
double t,xn,yn;
int z;
scanf("%d",&z);
scanf("%lf%lf",&xp,&yp);
scanf("%lf%lf%lf",&a,&b,&c);
scanf("%lf%lf",&xq,&yq);
t=asin(b/c);
if(z==0)
{
xn=xp*cos(t)-yp*sin(t)-xq*cos(t)+yq*sin(t)+xq;
yn=xp*sin(t)+yp*cos(t)-xq*sin(t)-yq*cos(t)+yq;
}
else
{
xn=xp*cos(t)+yp*sin(t)-xq*cos(t)-yq*sin(t)+xq;
yn=-xp*sin(t)+yp*cos(t)+xq*sin(t)-yq*cos(t)+yq;
}
printf("%0.lf %0.lf",xn,yn);
return 0;
}
This code gave correct output for both of the test cases provided in the question.
Do tell if it worked :)
Sorry I feel stupid asking this and am prepared to lose half of my points asking this but why does this algorithm not work? It works up to a point. After the number 13 the factorials are a little off. For instance the numbers do not entirely match in the hundreds thousands place and onward.
#include <stdio.h>
float factorial(unsigned int i) {
if (i <= 1) {
return 1;
}
return i * factorial(i - 1);
}
int main() {
int i = 13;
printf("Factorial of %d is %f\n", i, factorial(i));
return 0;
}
Here's the output:
Factorial of 13 is 6227020800.000000
Here is an example of inaccurate output:
Factorial of 14 is 87178289152.000000
The output for the number 14 should actually be this (from mathisfun.com)
14 87,178,291,200
I changed the return type to float to obtain more accurate output but I obtained this code for the most part from here: https://www.tutorialspoint.com/cprogramming/c_recursion.htm
EDIT: If I change to the return type to double the output is accurate up to 21.I am using the %Lf string formatter for the output in the printf function.
Simple. float cannot accurately store integers above 16777216 without loss of precision.
int is better than float. But try long long so you can properly store 19 digits.
OP is encountering the precision limits of float. For typical float, whole number values above 16777216.0f are not all exactly representable. Some factorial results above this point are exactly representable.
Let us try this with different types.
At 11!, the float results exceeds 16777216.0f and is exactly correct.
At 14!, the float result is imprecise because of limited precision.
At 23!, the double result is imprecise because of limited precision.
At 22!, the answer exceeds my uintmax_t range. (64-bit)
At 35!, the answer exceeds my float range.
At 171!, the answer exceeds my double range.
A string representation is accurate endlessly until it reaches buffer limitations.
#include <stdint.h>
#include <string.h>
#include <stdio.h>
uintmax_t factorial_uintmax(unsigned int i) {
if (i <= 1) {
return 1;
}
return i * factorial_uintmax(i - 1);
}
float factorial_float(unsigned int i) {
if (i <= 1) {
return 1;
}
return i * factorial_float(i - 1);
}
double factorial_double(unsigned int i) {
if (i <= 1) {
return 1;
}
return i * factorial_double(i - 1);
}
char * string_mult(char *y, unsigned base, unsigned x) {
size_t len = strlen(y);
unsigned acc = 0;
size_t i = len;
while (i > 0) {
i--;
acc += (y[i] - '0') * x;
y[i] = acc % base + '0';
acc /= base;
}
while (acc) {
memmove(&y[1], &y[0], ++len);
y[0] = acc % base + '0';
acc /= base;
}
return y;
}
char *factorial_string(char *dest, unsigned int i) {
strcpy(dest, "1");
for (unsigned m = 2; m <= i; m++) {
string_mult(dest, 10, m);
}
return dest;
}
void factorial_test(unsigned int i) {
uintmax_t u = factorial_uintmax(i);
float f = factorial_float(i);
double d = factorial_double(i);
char s[2000];
factorial_string(s, i);
printf("factorial of %3d is uintmax_t: %ju\n", i, u);
printf(" float: %.0f %s\n", f, "*" + (1.0 * f == u));
printf(" double: %.0f %s\n", d, "*" + (d == u));
printf(" string: %s\n", s);
}
int main(void) {
for (unsigned i = 11; i < 172; i++)
factorial_test(i);
return 0;
}
Output
factorial of 11 is uintmax_t: 39916800
float: 39916800
double: 39916800
string: 39916800
factorial of 12 is uintmax_t: 479001600
float: 479001600
double: 479001600
string: 479001600
factorial of 13 is uintmax_t: 6227020800
float: 6227020800
double: 6227020800
string: 6227020800
factorial of 14 is uintmax_t: 87178291200
float: 87178289152 *
double: 87178291200
string: 87178291200
factorial of 20 is uintmax_t: 2432902008176640000
float: 2432902023163674624 *
double: 2432902008176640000
string: 2432902008176640000
factorial of 21 is uintmax_t: 14197454024290336768
float: 51090940837169725440 *
double: 51090942171709440000 *
string: 51090942171709440000
factorial of 22 is uintmax_t: 17196083355034583040
float: 1124000724806013026304 *
double: 1124000727777607680000 *
string: 1124000727777607680000
factorial of 23 is uintmax_t: 8128291617894825984
float: 25852017444594485559296 *
double: 25852016738884978212864 *
string: 25852016738884976640000
factorial of 34 is uintmax_t: 4926277576697053184
float: 295232822996533287161359432338880069632 *
double: 295232799039604119555149671006000381952 *
string: 295232799039604140847618609643520000000
factorial of 35 is uintmax_t: 6399018521010896896
float: inf *
double: 10333147966386144222209170348167175077888 *
string: 10333147966386144929666651337523200000000
factorial of 170 is uintmax_t: 0
float: inf *
double: 72574156153079940453996357155895914678961840000000... *
string: 72574156153079989673967282111292631147169916812964...
factorial of 171 is uintmax_t: 0
float: inf *
double: inf *
string: 12410180702176678234248405241031039926166055775016...
Someone posted a similar question a while back. The consensus was if you're writing it for work use a big number library (like GMP) and if it's a programming exercise write up a solution using a character array.
For example:
/* fact50.c
calculate a table of factorials from 0! to 50! by keeping a running sum of character digits
*/
#include <stdio.h>
#include <string.h>
int main (void)
{
printf ("\n Table of Factorials\n\n");
// length of arrays = 65 character digits
char str[] =
"00000000000000000000000000000000000000000000000000000000000000000";
char sum[] =
"00000000000000000000000000000000000000000000000000000000000000001";
const int len = strlen (str);
int index;
for ( int i = 0; i <= 50; ++i ) {
memcpy (str, sum, len);
for ( int j = 1; j <= i - 1; ++j ) {
index = len - 1;
int carry = 0;
do {
int digit = (sum[index] - '0') + (str[index] - '0') + carry;
carry = 0;
if ( digit > 9 ) {
carry = 1;
digit %= 10;
}
sum[index] = digit + '0';
--index;
}
while ( index >= 0 );
}
printf ("%2i! = ", i);
for ( index = 0; sum[index] == '0'; ++index )
printf ("%c", '.');
for ( ; index < len; ++index )
printf ("%c", sum[index]);
printf ("\n");
}
return 0;
}
Why Is This Factorial Algorithm Not Accurate
There's nothing wrong in your algorithm as such. It is just that the data types you use have a limit for the highest number they can store. This will be a problem no matter which algorithm you choose. You can change the data types from float to something like long double to hold something bigger. But eventually it will still start failing once the factorial value exceeds the capacity of that data type. In my opinion, you should put an a condition in your factorial function to return without calculating anything if the passed in argument is greater than a value that your chosen datatype can support.
float can represent a wider range of numbers than int, but it cannot represent all the values within that range - as you approach the edge of the range (i.e., as the magnitudes of the values increase), the gap between representable values gets wider.
For example, if you cannot represent values between 0.123 and 0.124, then you also cannot represent values between 123.0 and 124.0, or 1230.0 and 1240.0, or 12300.0 and 12400.0, etc. (of course, IEEE-754 single-precision float gives you a bit more precision than that).
Having said that, float should be able to represent all integer values up to 224 exactly, so I'm going to bet the issue is in the printf call - float parameters are "promoted" to double, so there's a representation change involved, and that may account for the lost precision.
Try changing the return type of factorial to double and see if that doesn't help.
<gratuitous rant>
Every time I see a recursive factorial function I want to scream. Recursion in this particular case offers no improvement in either code clarity or performance over an iterative solution:
double fac( int x )
{
double result = 1.0;
while ( x )
{
result *= x--;
}
return result;
}
and can in fact result in worse performance due to the overhead of so many function calls.
Yes, the definition of a factorial is recursive, but the implementation of a factorial function doesn't have to be. Same for Fibonacci sequences. There's even a closed form solution for Fibonacci numbers
Fn = ((1 + √5)n - (1 - √5)n) / (2n * √5)
that doesn't require any looping in the first place.
Recursion's great for algorithms that partition their data into relatively few, equal-sized subsets (Quicksort, tree traversals, etc.). For something like this, where the partitioning is N-1 subsets of 1 element? Not so much.
</gratuitous rant>
I am very new to C programming and I am writing a program which takes a number which is suppose to be 9 digits long. After this I multiply each digit with either 1 or 2. I am using arrays to ask user to enter their numbers. I would like to know if there is a way to multiply those 9 numbers with different numbers as one integer instead of using arrays? Here is my code with arrays:
#include <stdio.h>
int main(void) {
int sin_num[9];
int num1;
int num2, num11, num12;
int num3, num4, num5, num6, num7, num8, num9, num10;
for(num1=0; num1<9; num1++) {
printf("Enter your SIN number one by one:");
scanf("%d", &sin_num[num1]);
}
num2 = sin_num[0] * 1;
num3 = sin_num[1] * 2;
num4 = sin_num[2] * 1;
num5 = sin_num[3] * 2;
num6 = sin_num[4] * 1;
num7 = sin_num[5] * 2;
num8 = sin_num[6] * 1;
num9 = sin_num[7] * 2;
num10 = sin_num[8] * 1;
Right now I am doing this:
element 1 * 1
element 2 * 2
element 3 * 1
But how can I do, lets say if I enter 123456789 multiply with different numbers:
123456789
121212121
Well I couldn't much understand what you were asking. Anyways hope this is what you are looking for.....
#include<stdio.h>
int main()
{
long int nine_digit_num;
int step=100000000;
int digit,input_num,i;
printf("Enter 9 digit number:\n");
scanf("%ld",&nine_digit_num);
for(i=1;i<=9;i++)
{
printf("Enter a number to multiply with the %d digit:\n",i);
scanf("%d",&input_num);
digit=nine_digit_num/step; // this and the next step are used to
digit=digit%10; // obtain the individual digits.
printf("%d*%d=%d\n",digit,input_num,digit*input_num);
step=step/10;
}
return 0;
}
I'm sure there are Luhn algorithm solutions already written that you could reference, but I'm going to invent my own right now just to have a walkthrough.
Since your input is only 9 digits, it will fit in a plain 32 bit variable. I'll use unsigned on the assumption it's 32 bits or bigger, but for production code, you'd likely want to use inttypes.h uint32_t and associated scanf macros.
#include <stdio.h>
int main(void) {
unsigned sin_num, checksum, digit;
int i;
printf("Enter your SIN as a 9 digit number using only digits:\n");
if (scanf(" %9u", &sin_num) < 1) ... do error handling or just exit ...
for (i = 0; sin_num; ++i) {
digit = sin_num % 10;
sin_num /= 10;
if (i & 1) { // Double odd digits (might have this backwards; check me for your case
digit *= 2;
if (digit >= 10) digit = digit % 10 + digit / 10; // Luhn carry is strange
}
checksum += digit;
}
... do whatever else you need to do ...
It's not a single mathematical operation because Luhn's carry is too weird for magic number tricks, but it's still much more straightforward than a bunch of single digit scanf calls and array storage.