How to compare extracted digits in C++ - c++

Question

I'm trying to implement the Bulls & Cows game and I have a logic problem. I am explicitly checking if each digit is either equal to a digit in the corresponding index (bulls) or at other indexes (cows). The value that I check with (4321) should yield "0 bulls and 4 cows" but it instead gives me "0 bulls and 3 cows.
Here is my code (and I apologize for the code repetition. I am also wondering if anyone has recommendations to make this code smaller):
#include <iostream>
#include <vector>
using namespace std;
int main() {
int guessValue = 1234;
int guess;
int bulls = 0;
int cows = 0;
cout << "Enter a 4 digit guess: ";
cin >> guess;
int firstValue = (guess % 10000) / 1000;
int secondValue = (guess % 1000) / 100;
int thirdValue = (guess % 100) / 10;
int fourthValue = guess % 10;
if (firstValue == ((guessValue % 10000) / 1000)) {bulls += 1;}
else if(firstValue == ((guessValue % 1000) / 100) ||
firstValue == ((guessValue % 100) / 10) ||
firstValue == (guess % 10))
{cows += 1;}
if (secondValue == ((guessValue % 1000) / 100)) {bulls += 1;}
else if (secondValue == ((guessValue % 10000) / 1000) ||
secondValue == ((guessValue % 100) / 10) ||
secondValue == (guess % 10))
{cows += 1;}
if (thirdValue == ((guessValue % 100) / 10)) {bulls += 1;}
else if (thirdValue == ((guessValue % 10000) / 1000) ||
thirdValue == ((guessValue % 1000) / 100) ||
thirdValue == (guess % 10))
{cows += 1;}
if (fourthValue == (guessValue % 10)) {bulls += 1;}
else if (fourthValue == ((guessValue % 10000) / 1000) ||
fourthValue == ((guessValue % 1000) / 100) ||
fourthValue == (guessValue % 100) / 10)
{cows += 1;}
cout << bulls << " bulls and " << cows << " cows" << endl;
}

Answer 1

I am also wondering if anyone has recommendations to make this code smaller
First of all use std::vector to keep separate digits:
std::vector<int> split( int v )
{
std::vector<int> r;
while( v ) {
r.push_back( v % 10 );
v /= 10;
}
return r;
}
Second, use standard algo std::count_if:
auto bulls = std::count_if( guessv.begin(), guessv.end(),
[it = targetv.begin()]( int i ) mutable
{ return i == *it++; } );
auto cows = std::count_if( guessv.begin(), guessv.end(),
[s = std::set<int>{ targetv.begin(), targetv.end() }]( int i )
{ return s.count( i ); } );
second one is actually counts cows and bulls, so it needs to be adjusted:
cows -= bulls;
live example

Answer 2

2 concepts that absolutely you need to master: loops and functions. First create some helpful functions.
These are the functions you could built your program upon:
int get_digit(int number, int order)
with example test cases:
get_digit(7895, 0) == 5
get_digit(7895, 1) == 9
get_digit(7895, 2) == 8
get_digit(7895, 3) == 7
then:
bool has_digit(int number, int digit)
with example test cases:
has_digit(7895, 1) == false
has_digit(7895, 8) == true
has_digit(7895, 5) == true
has_digit(7895, 0) == false
has_digit(7000, 0) == true
then:
bool matches_digit(int a, int b, int order)
with test cases:
matches_digit(1239, 4269, 0) == true
matches_digit(1239, 4269, 1) == false
matches_digit(1239, 4269, 2) == true
matches_digit(1239, 4269, 2) == false
and finally:
int get_cow(int a, int b)
int get_bull(int a, int b)
int main()
This is a top-down design, bottom-up implementation approach. First you think of the big picture and figure out what small pieces you need (functions) and then start implementing from the smallest most independent functions and step by step combine then into higher functions until you reach main.

Answer 3

This is my solution and it works. Basically I had to create a function to extract each digit and store them into a vector that can be applied to both the model and the guess. Then I used the find() method of the <algorithm> library to see if the digits exist in the guess vector and if yes, at which position compared to the model vector. Same position equals 1 bull and different position equals 1 cow. I am going to add more to this program, such as generating the model randomly and looping the program after each round so the user doesn't have to restart the game.
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
vector<int> getDigits(int modelValue) {
vector<int> vectorValue;
int extractedDigit = 0;
int modulant = 10000;
int divisor = 1000;
for (int i = 0; i < 4; i++) {
extractedDigit = (modelValue % modulant) / divisor;
vectorValue.push_back(extractedDigit);
modulant /= 10;
divisor /= 10;
}return vectorValue;
}
int main() {
int model = 1234;
int guess = 0000;
int bulls = 0;
int cows = 0;
int counter = 1;
cout << "Enter a value to guess: ";
cin >> guess;
vector<int> modelVector = getDigits(model);
vector<int> guessVector = getDigits(guess);
for (int i = 0; i < 4; i++) {
if (find(modelVector.begin(), modelVector.end(), guessVector[i]) != modelVector.end()) {
if (modelVector[i] == guessVector[i]) {bulls += 1;}
else { cows += 1; }
}
}cout << "There are " << bulls << " bulls and " << cows << " cows"<< endl;
}