str and int

#include <iostream>

using namespace std;

int str2i(char* ch)
{
    int val = 0;
    for (int i = 0; ch[i] != '\0'; i++) {
        val = val * 10 + ch[i] - '0';
    }
    return val;
}

void i2str(char* ch, int n)
{
    if (n == 0) {
        ch[0] = '0';
        ch[1] = '\0';
    } else {
        int digits[80] = { 0 };
        int ord = 0;

        while (n > 0) {
            digits[ord++] = n % 10;
            n /= 10;
        }

        ch[ord] = '\0';

        for (int i = 0; i < ord; i++) {
            ch[i] = digits[ord - 1 - i] + '0';
        }
    }
}

int main()
{
    char buffer[80] = { '\0' };

    int n = 0;
    i2str(buffer, n);
    cout << buffer << endl;
    cout << str2i(buffer) << endl;

    n = 1;
    i2str(buffer, n);
    cout << buffer << endl;
    cout << str2i(buffer) << endl;

    n = 29876543;
    i2str(buffer, n);
    cout << buffer << endl;
    cout << str2i(buffer) << endl;
}