Hexadecimal string to decimal number

Write a program to convert hexadecimal string to decimal number

The solution:-

#include <iostream>
using namespace std;

int main() {
    char input[] = "64";
    int val = 0;
    char* ptr = input;
    while ( *ptr != '' ) {
         val = val * 16 + *ptr - '0';
         ptr++;
    }
    cout << val << endl;
    return 0;
}

Output:-

100