N进制到M进制-C语言

//N进制到M进制 
//N进制先转换为十进制，十进制在转换为M进制
#include <stdio.h>
#include <string.h>
#define N 2
#define M 16
int NToD(const char *a, int len, int base);
void DToM(int d, int m, char *Mnum);
int main()
{char Nnum[20], Mnum[20];gets(Nnum);int len = strlen(Nnum);int sum = NToD(Nnum, len, N);DToM(sum, M, Mnum);printf("%s", Mnum);return 0;
} //转十进制 
int NToD(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;elsesum += (a[i] - '0')*weight;weight *=  base;}return sum;
}
//十进制转二进制 
void DToM(int d, int m, char *Mnum)
{int len = 0, r;char temp;do{r = d % m;  //只存余数 if(r >= 10)Mnum[len++] = r - 10 + 'a';elseMnum[len++] = r + '0';d = d / m;  //用于再次求余 }while(d != 0);Mnum[len] = '\0';for(int i = 0, j = len - 1; i < j; i++, j--){temp = Mnum[i]; Mnum[i] = Mnum[j]; Mnum[j] = temp;} 
}