I've written some code in C to try adn find whether or not a number is a Palindrome. The rule is that two 3 digit numbers have to be multiplied together and you have to find the highest palindrome. the answer should be 906609 but my code only gets to 580085.
the code:
#include <stdio.h>
#include <stdlib.h>
/* Intialise */
void CalcPalin();
int CheckPalin(int number);
/* Functions */
void CalcPalin()
{
int result = 0;
int palin = 0;
int FNumber = 0;
int FNumber2 = 0;
int number = 99;
int number2 = 100;
while(number2 < 1000)
{
number += 1;
/*times together - calc result*/
result = number * number2;
if(CheckPalin(result) == 1)
{
palin = result;
FNumber = number;
FNumber2 = number2;
}
if(number == 999)
{
number = 99;
number2 += 1;
}
}
printf(" Result = %d, by Multiplying [%d] and [%d]", palin, FNumber, FNumber2 );
}
int CheckPalin(int number)
{
int checknum, checknum2 = 0;
checknum = number;
while(checknum)
{
checknum2 = checknum2 * 10 + checknum % 10;
checknum /= 10;
}
if( number == checknum2)
return 1;
else
return 0;
}
int main( void)
{
CalcPalin();
return EXIT_SUCCESS;
}
Im pretty sure its a stupid answer and im over looking something simple but i cant seem to find it. Any help would be great
You have not tested whether the current result is higher than one old result. Add this check.
// test new result is higher than old palin before setting this as palin
if(CheckPalin(result) == 1 && palin < result)
Your algorithm print :
Result = 580085, by Multiplying [583] and [995]
It seems that you should find a way to increment more the 1st number. There is many possibility between 583 and 999 in order to get to 906609.
EDIT : In fact, you are looking for 993 * 913 = 906609.
Related
this is my code, I want to make a function that when it is called will generate a number between 1111 to 9999, I don't know how to continue or if I've written this right. Could someone please help me figure this function out. It suppose to be simple.
I had to edit the question in order to clarify some things. This function is needed to get 4 random digits that is understandable from the code. And the other part is that i have to make another function which is a bool. The bool needs to first of get the numbers from the function get_random_4digits and check if there contains a 0 in the number. If that is the case then the other function, lets call it unique_4digit, should disregard of that number that contained a 0 in it and check for a new one to use. I need not help with the function get_random_4digitsbecause it is correct. I need helt constructing a bool that takes get_random_4digits as an argument to check if it contains a 0. My brain can't comprehend how I first do the get_random_4digit then pass the answer to unique_4digits in order to check if the random 4 digits contains a 0 and only make it print the results that doesn't contain a 0.
So I need help with understanding how to check the random 4 digits for the integer 0 and not let it print if it has a 0, and only let the 4 random numbers print when it does not contain a 0.
the code is not suppose to get more complicated than this.
int get_random_4digit(){
int lower = 1000, upper = 9999,answer;
answer = (rand()%(upper-lower)1)+lower;
return answer;
}
bool unique_4digits(answer){
if(answer == 0)
return true;
if(answer < 0)
answer = -answer;
while(answer > 0) {
if(answer % 10 == 0)
return true;
answer /= 10;
}
return false;
}
printf("Random answer %d\n", get_random_4digit());
printf("Random answer %d\n", get_random_4digit());
printf("Random answer %d\n", get_random_4digit());
Instead of testing each generated code for a disqualifying zero just generate a code without zero in it:
int generate_zero_free_code()
{
int n;
int result = 0;
for (n = 0; n < 4; n ++)
result = 10 * result + rand() % 9; // add a digit 0..8
result += 1111; // shift each digit from range 0..8 to 1..9
return result;
}
You can run the number, dividing it by 10 and checking the rest of it by 10:
int a = n // save the original value
while(a%10 != 0){
a = a / 10;
}
And then check the result:
if (a%10 != 0) printf("%d\n", n);
Edit: making it a stand alone function:
bool unique_4digits(int n)
{
while(n%10 != 0){
n = n / 10;
}
return n != 0;
}
Usage: if (unique_4digits(n)) printf("%d\n", n);
To test if the number doesn't contain any zero you can use a function that returns zero if it fails and the number if it passes the test :
bool FourDigitsWithoutZero() {
int n = get_random_4digit();
if (n % 1000 < 100 || n % 100 < 10 || n % 10 == 0) return 0;
else return n;
}
"I need not help with the function get_random_4digits because it is correct."
Actually the following does not compile,
int get_random_4digit(){
int lower = 1000, upper = 9999,answer;
answer = (rand()%(upper-lower)1)+lower;
return answer;
}
The following includes modifications that do compile, but still does not match your stated objectives::
int get_random_4digit(){
srand(clock());
int lower = 1000, upper = 9999,answer;
int range = upper-lower;
answer = lower + rand()%range;
return answer;
}
" I want to make a function that when it is called will generate a number between 1111 to 9999,"
This will do it using a helper function to test for zero:
int main(void)
{
printf( "Random answer %d\n", random_range(1111, 9999));
printf( "Random answer %d\n", random_range(1111, 9999));
printf( "Random answer %d\n", random_range(1111, 9999));
printf( "Random answer %d\n", random_range(1111, 9999));
return 0;
}
Function that does work follows:
int random_range(int min, int max)
{
bool zero = true;
char buf[10] = {0};
int res = 0;
srand(clock());
while(zero)
{
res = min + rand() % (max+1 - min);
sprintf(buf, "%d", res);
zero = if_zero(buf);
}
return res;
}
bool if_zero(const char *num)
{
while(*num)
{
if(*num == '0') return true;
num++;
}
return false;
}
I want to make a program to count the sum of digits in a string but only using stdio.h
but the program needs to count until its less than 10
so the example you input 56 it would be 5+6=11 then 1+1=2 and so on
here's my code. For now I'm just confused how to check if its whether more than 9 or not
#include<stdio.h>
int plus(int n);
int main(void)
{
int n, digit, test;
scanf("%d", &n);
test = plus(n);
while(test != 0)
{
if(test > 9)
plus(test);
else
break;
}
printf("%d", test);
}
int plus(int n)
{
int digit=0,test=0;
while(n != 0)
{
digit = n%10;
test = test + digit;
n = n/10;
}
return test;
}
You are not storing the value returned by plus function in the while body.
You can change the condition in while to check whether it is greater than 9 or not, and assign test as test = plus(test);
So, your while will look like this.
while(test > 9)
{
test=plus(test);
}
You need to recursively call the function plus() until the value returned by it becomes less than 10. Like shown below:
int main(void)
{
int n=56;
while(n> 10)
{
n = plus(n);
}
printf("%d", n);
}
I am working on a game of Yahtzee and one part of the game is the user can choose which dice out of 5 they wish to re-roll. I don't really know how to approach this besides writing a ton of if if-else statements, but there has to be a more efficient way to re-roll the specific die/ dice. I wrote out a snippet of what I am trying to accomplish, its not exactly like this in my actual code, but hopefully it is enough to answer the question :)
#include<stdio.h>
int main(void)
{
int die1 = 0, die2 = 0, die3 = 0, die4 = 0, die5 = 0;
int *ptr_die1 = &die1, *ptr_die2 = &die2, *ptr_die3 = &die3, *ptr_die4 = &die4, *ptr_die5 = &die5;
int choice = 0;
int die[5] = { 0 };
for (int i = 0; i < 5; i++)
{
die[i] = rand() % 6 + 1;
}
printf("Die[1] = %d\n", die[0]);
printf("Die[2] = %d\n", die[1]);
printf("Die[3] = %d\n", die[2]);
printf("Die[4] = %d\n", die[3]);
printf("Die[5] = %d\n", die[4]);
choice = printf("Please select which die to reroll\n");
scanf("%d", &choice);
printf("%d\n", choice);
for (int i = 0; i < 5; i++)
{
die[choice-1] = rand() % 6 + 1;
}
printf("Die[1] = %d\n", die[0]);
printf("Die[2] = %d\n", die[1]);
printf("Die[3] = %d\n", die[2]);
printf("Die[4] = %d\n", die[3]);
printf("Die[5] = %d\n", die[4]);
return 0;
}
after this I am really lost on how to change the die because the user could want to change just 1, or all 5 or any combination in between...
You have way too many variables that are not really needed.
int main(int argc, char **argv)
{
int i;
int choice;
int dices[5];
srand(time(NULL));
while(1){
for (i = 0; i < 5; i++)
dices[i] = rand() % 6 + 1;
choice = printf("Please select which die to reroll (or enter 0 to quit)");
scanf("%d", &choice);
if (choice == 0) // end the game
break;
if (choice < 1 || choice > 5 ){ // make sure that input is valid
fprintf(stderr, "error, input should be between 1 to 5 (inclusive)\n");
return -1;
}
printf("dice shows: %d", dices[choice-1]);
}
return 0;
}
You need to ask the user for the ending it, e.g. "Enter 0 to end the game". Otherwise it would be an infinite loop.
You could have the user input a comma-separatd list of die, instead of a single integer, which it looks like you're doing now. Then just parse the input, check that you have between 1 and 5 valid integers less than 6, and index into each die.
Or you could do like kaylum suggested and loop until the user inputs a special string indicating they're done, or prompt for 1, 2, ... 5 and ask for a yes or no answer to each.
Just use an array of int values to represent the set of dice:
#define DICE_COUNT 6
void rollDice(int* diceArray, size_t diceIndex) {
assert( 0 <= diceIndex && diceIndex < DICE_COUNT );
diceArray[ diceIndex ] = rand() % 6 + 1;
}
int main(int argc, char* argv[]) {
// Seed the RNG:
srand( (unsigned)time(&t) );
int dice[DICE_COUNT];
for(size_t i = 0; i < DICE_COUNT; i++) {
rollDice( dice, i );
}
while( true ) {
printf("Please select which die to reroll. Enter -2 to quit. (%d to %d inclusive)", 1, DICE_COUNT);
int selection = -1;
scanf("%d", &selection);
if( selection == -2 ) break;
if( 1 <= selection && selection <= DICE_COUNT ) {
selection--; // convert from 1-6 to 0-5.
rollDice( dice, selection );
}
}
return EXIT_SUCCESS;
}
I don't see any if..else statements in your code above. I will say, in this chunk of code:
for (int i = 0; i < 5; i++)
{
die[choice-1] = rand() % 6 + 1;
}
You don't need the for loop. You are not using the index, and rand() should work the first time through. I know rand() isn't the best written function, but if you seed it first, it should give you a pseudo-random number.
#include <time.h>
...
/* initialize random seed: */
srand ( time(NULL) );
...
die[choice-1] = rand() % 6 + 1;
Hope this was helpful, if you are still even working on that project!
I'm trying to succeed with project euler's 4th problem : What is the biggest palindrome-number you can make by multiplying 2 3-digit numbers ?
( https://projecteuler.net/problem=4 )
I have the following code but it is not working. For some reason it seems like the nested while loop is broken. It only print numbers 10000 to 99900, which means the nested while loop is executed only once...
#include <stdio.h>
#include <string.h>
int is_a_palindrome(int test_number);
int main (void)
{
long result;
long number_x_1;
long number_x_2;
long biggest_pal;
number_x_1 = 100;
number_x_2 = 100;
while (number_x_1 < 1000)
{
while (number_x_2 < 1000)
{
result = number_x_1 * number_x_2;
printf("%li\n", result);
if (is_a_palindrome(result) == 1)
{
biggest_pal = result;
printf("palindrome found : %li", biggest_pal);
}
number_x_2++;
}
number_x_1++;
}
return (biggest_pal);
}
int is_a_palindrome(int test_number)
{
int test_number_unchanged;
int reverse;
reverse = 0;
test_number_unchanged = test_number;
while (test_number != 0)
{
reverse = reverse * 10;
reverse = reverse + test_number % 10;
test_number = test_number / 10;
}
if (test_number_unchanged == reverse)
{
return (1);
}
else
{
return (0);
}
}
You don't set number_x_2 to 100 inside the outer loop... you do it only once outside all loops !
Thus when the 2nd loop on number_x_1 starts, number_x_2 is already at the maximum value and the inside loop (at while (number_x_2 < 1000)) does not start.
Check that simple mistake.. you must initialize number_x_2 = 100 in outer loop..
#include <stdio.h>
#include <string.h>
int is_a_palindrome(int test_number);
int main (void)
{
long result;
long number_x_1;
long number_x_2;
long biggest_pal;
number_x_1 = 100;
while (number_x_1 < 1000)
{
number_x_2 = 100;
while (number_x_2 < 1000)
{
result = number_x_1 * number_x_2;
printf("%li\n", result);
if (is_a_palindrome(result) == 1)
{
biggest_pal = result;
printf("palindrome found : %li", biggest_pal);
}
number_x_2++;
}
number_x_1++;
}
return (biggest_pal);
}
int is_a_palindrome(int test_number)
{
int test_number_unchanged;
int reverse;
reverse = 0;
test_number_unchanged = test_number;
while (test_number != 0)
{
reverse = reverse * 10;
reverse = reverse + test_number % 10;
test_number = test_number / 10;
}
if (test_number_unchanged == reverse)
{
return (1);
}
else
{
return (0);
}
}
The inner while loop sends number_x_2 to 1000, but then it stays at 1000 so the program never runs through the inner loop after the first cycle. The program then increments number_x_1 until it reaches 1000, and the program ends.
To solve this, move the statement number_x_2 = 100; To the line before while(number_x_2 < 1000).
I'm trying to solve Problem 4 -Project Euler and I am stucked. So I need a little help with my code. Here is the problem I am trying to solve:
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Find the largest palindrome made from the product of two 3-digit numbers.
Code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int is_palindrom(int number, int revrse) {
char str1[6];
char str2[6];
sprintf(str1, "%d", number);
sprintf(str2, "%d", revrse);
return strcmp(str1, str2);
}
int main(void) {
int number, revrse;
int i, j, temp;
int maks;
for(i=999;i>99;i--)
for(j=999;j>99;j--) {
temp = number = i*j;
while (temp != 0) {
revrse = revrse * 10;
revrse = revrse + temp%10;
temp = temp/10;
}
if(is_palindrom(number, revrse)==0 && number > maks)
maks = number;
}
printf("%d",maks);
return 0;
}
The revrse var isn't initialized so there are rubbish in it. Remember to always init a variable!
Complementing the answer from #kleszcz, revrse must always be initialized before the while loop begins, otherwise, it will hold the previous value (and rubbish in the first iteration, as he intelligently pointed out).
Another issue is that you do not need the is_palindrome function. You can check directly if the numbers are equal.
To get the reversed form of your number properly, you need to first set an initial value for revrse of 0 for each iteration of your loop, otherwise the behavior is undefined. It also helps to set an initial value for maks to compare against. Finally, why use a function to check for palindromes when you can just check for equality between your number and its reverse?
int main()
{
int number;
int i,j,temp;
int maks = -1;
int revrse;
for(i=999;i>99;i--) {
for(j=999;j>99;j--) {
number = i*j;
revrse = 0;
temp=number;
while (temp != 0){
revrse = revrse * 10;
revrse = revrse + temp%10;
temp = temp/10;
}
if(number == revrse) {
if(number > maks) {
maks = number;
}
}
}
}
printf("%d",maks);
return 0;
}