String to integers using recursion

string_to_integer_recursion.cpp

#include <iostream>
using namespace std;
#include <cmath>

int number(char input[], int size){
    if (size < 1){
        return 0;
    }
    int sum = number(input+1, size-1);
    int i = input[0];
    i = i-48;
    return sum + i*pow(10,size-1);
}

int size(char input[]){
    int i = 0;
    while(input[i]){
        i++;
    }
    return i ; 
}

int stringToNumber(char input[]) {
    int length = size(input);
    int sum = number(input, length);
    return sum ; 
}

int main() {
    char input[50];
    cin >> input;
    cout << stringToNumber(input) << endl;
}