How to split a number into digits in C++ [duplicate] - c++

Question

This question already has answers here:
Converting integer into array of digits [closed]
(4 answers)
Closed 2 years ago.
I know there are similar questions on Stack overflow about this. I already checked them. Here are two points:
The number will be an input from the user, so I won't know how many digits the number may actually contain
I DON'T want to directly print the digits, I need to do some further process on every digit, so I need a way to save or assign every single digit.
So fore example, if the user enters 1027, I'll need 1, 0, 2, 7 returned, and not printed. That's where my problem starts.
Here's how I'd write it if it could be printed:
int x;
cin>>x;
while(x != 0)
{
cout<<x%10<<endl;
x/=10;
}
Any hints or help is in advance appreciated.

Answer 1

It depends what order you need it in. If you need least-significant digit (rightmost) to most-significant (leftmost), then your solution is almost there
int x = ...
while(x != 0)
{
int current = x % 10; // get rightmost digit
x /= 10;
// process 'current', or store in a container for later processing
}
If you need most-significant (leftmost) to least-significant (rightmost), then you can do this recursively:
void for_each_digit(int input)
{
// recursive base case
if (input == 0) { return; };
int current = input % 10
for_each_digit(input / 10); // recurse *first*, then process
// process 'current', add to container, etc
}
// ...
int x = ...
for_each_digit(x);
Edit: I apparently missed the part about returning a sequence of digits.
Either approach works. If you go right-to-left, you will need to reverse the container first. If you go recursive, you will need to append each value to the container.

Answer 2

Use a std::string:
std::string input;
std::cin >> input;
Now input[i] is the i-th digit. input.size() is the number of digits.

Answer 3

Well you can use vector. It can take variable length input. You need not declare the size beforehand. Learn more about vector here: vector
#include<iostream>
#include<vector>
#include <algorithm> // std::reverse
using namespace std;
int main(void)
{
vector<int>digits;
int x;
cin >> x;
while(x)
{
digits.push_back(x % 10);
x = x / 10;
}
// reversing the order of the elements inside vector "digits" as they are collected from last to first and we want them from first to last.
reverse(digits.begin(), digits.end());
// Now the vector "digits" contains the digits of the given number. You can access the elements of a vector using their indices in the same way you access the elements of an array.
for(int i = 0; i < digits.size(); i++) cout << digits[i] << " ";
return 0;
}

Answer 4

You may try std::vector<int> to store unknown number of integers as shown:
#include <iostream>
#include <vector>
int main(void) {
std::vector<int> digits;
std::string s;
std::cout << "Enter the number: ";
std::cin >> s;
size_t len = s.length();
for (size_t i = 0; i < len; i++) {
digits.push_back(s[i] - '0');
}
// Comment next 3 code to stop getting output
for (size_t i = 0; i < len; i++)
std::cout << digits[i] << ' ';
std::cout << std::endl;
return 0;
}
Note: This approach doesn't performs any mathematical operations (i.e. operation of division and getting remainders). It simply stores each integer in a vector using a for loop.