N进制转十进制-C语言

//N进制到十进制 
#include <stdio.h>
#include <string.h>
#define N 8
int NToDec1(const char *a, int len, int base);
int NToDec2(const char *a, int len, int base);
int main()
{
	char number_oc[20];
	gets(number_oc);
	int sum = 0;
	int len = strlen(number_oc);
	sum = NToDec2(number_oc, len, N);
	printf("%d\n", sum);
	return 0;
} 
//从左往右取值 
int NToDec1(const char *a, int len, int base)
{
	int sum = 0;
	for(int i = 0; i < len; i++)
	{
		//主要 
		if(a[i] >= 'a' && a[i] <= 'z')
			sum = sum * N + a[i] - 'a' + 10;
		else if(a[i] >= 'A' && a[i] <= 'Z')
			sum = sum * N + a[i] - 'A' + 10;
		else
			sum = sum * N + a[i] - '0';
	}
	return sum;
} 
//从右往左取值 
int NToDec2(const char *a, int len, int base)
{
	int sum = 0;
	int weight = 1;
	for(int i = len - 1; i >= 0; i--)
	{
		//主要 
		if(a[i] >= 'a' && a[i] <= 'z')
			sum += (a[i] - 'a' + 10)*weight;
		else if(a[i] >= 'A' && a[i] <= 'Z')
			sum += (a[i] - 'A' + 10)*weight;
		else
			sum += (a[i] - '0')*weight;
		weight *=  base;
	}
	return sum;
}