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// C program to convert a number from any base
// to decimal
#include <stdio.h>
#include <string.h>
#include <iostream>
// To return value of a char. For example, 2 is
// returned for '2'. 10 is returned for 'A', 11
// for 'B'
int val(char c)
{
if (c >= '0' && c <= '9')
return (int)c - '0';
else
return (int)c - 'A' + 10;
}
// Function to convert a number from given base 'b'
// to decimal
int toDeci(char *str, int base)
{
int len = strlen(str);
int power = 1; // Initialize power of base
int num = 0; // Initialize result
int i;
// Decimal equivalent is str[len-1]*1 +
// str[len-1]*base + str[len-1]*(base^2) + ...
for (i = len - 1; i >= 0; i--)
{
// A digit in input number must be
// less than number's base
if (val(str[i]) >= base)
{
printf("Invalid Number");
return -1;
}
num += val(str[i]) * power;
power = power * base;
}
return num;
}
// Driver code
int main()
{
char str[] = "11A";
int base = 16;
printf("Please enter number followed by base: ");
std::cin >> str >> base;
printf("Decimal equivalent of %s in base %d is"
" %d\n",
str, base, toDeci(str, base));
return 0;
}
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