C语言：二进制数转换为十进制数

[Big_Data_1203]

题目描述： 输入一个n位的二进制数，先输入高位。然后输出对应的十进制数。例如：输入如下 5 11011 5表示二进制数有5位，11011是二进制数，那么输出为 二进制序列(11011)的值为:27 输入 5 11011 输出 二进制序列(11011)的值为:27 样例输入 5 11011 样例输出 二进制序列(11011)的值为:27 程序如下： #include <stdio.h> void main() { int n,twn,ten=0; int a,b,c,d,e; scanf("%d%d",&n,&twn); if(n>4) { a=twn/10000; b=twn%10000/1000; c=twn%1000/100; d=twn%100/10; e=twn%10; ten=a*16+b*8+c*4+d*2+e; } else if(n>3) { a=twn/1000; b=twn%1000/100; c=twn%100/10; d=twn%10; ten=a*8+b*4+c*2+d; } else if(n>2) { a=twn/100; b=twn%100/10; c=twn%10; ten=a*4+b*2+c; } else if(n>1) { a=twn/10; b=twn%10; ten=a*2+b; } else if(n>0) { ten=twn; } printf("二进制序列(%d)的值为:%d\n",twn,ten); }

[qzjhjxj]

当输入超过5位时，计算出错，修改如下，供参考：

#include <stdio.h>
void main()
{
    int n,twn,ten=0,v=1;//权值
    int a,b,c,d,e;
    scanf("%d%d",&n,&twn);
    b=twn;
    while(n--){
          a = b % 10;
          ten += a*v;
          v *= 2;
          b /= 10;
    }
   /*if(n>4)
    {
        a=twn/10000;
        b=twn%10000/1000;   
        c=twn%1000/100;
        d=twn%100/10;
        e=twn%10;
        ten=a*16+b*8+c*4+d*2+e;   
    }
    else if(n>3)
    {
        a=twn/1000;
        b=twn%1000/100;
        c=twn%100/10;
        d=twn%10;
        ten=a*8+b*4+c*2+d;      
    }
    else if(n>2)
    {
        a=twn/100;
        b=twn%100/10;
        c=twn%10;
        ten=a*4+b*2+c;
    }
    else if(n>1)
    {
        a=twn/10;
        b=twn%10;
        ten=a*2+b;
    }
    else if(n>0)
    {
        ten=twn;
    }*/
    printf("二进制序列(%d)的值为:%d\n",twn,ten);
    
}

[赵4老师]

仅供参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <locale.h>
int main() {
    int i,v;
    char bs[33];
    char b[33];
    char hs[9];
    char h[9];
    char s[4];
    char *e;

// 十进制整数转二进制串；
    i=1024;
    ltoa(i,b,2);
    sprintf(bs,"%032s",b);
    printf("i=%d,bs=%s\n",i,bs);
// 十进制整数转十六进制串；
    i=1024;
    ltoa(i,h,16);
    sprintf(hs,"%08s",h);
    printf("i=%d,hs=%s\n",i,hs);
// 十六进制字符串转成十进制数
    strcpy(hs,"00000400");
    sscanf(hs,"%x",&i);
    printf("hs=%s,i=%d\n",hs,i);
// 二进制字符串转化为十六进制字符串；
    strcpy(bs,"00000000000000000000010000000000");
    i=strtol(bs,&e,2);
    ltoa(i,h,16);
    sprintf(hs,"%08s",h);
    printf("bs=%s,hs=%s\n",bs,hs);
// 二进制字符串转化为十进制数；
    strcpy(bs,"00000000000000000000010000000000");
    i=strtol(bs,&e,2);
    printf("bs=%s,i=%d\n",bs,i);
// 十六进制字符串转成二进制串
    strcpy(hs,"00000400");
    sscanf(hs,"%x",&i);
    ltoa(i,b,2);
    sprintf(bs,"%032s",b);
    printf("hs=%s,bs=%s\n",hs,bs);
// ASC\GBK字符串转十六进制串
    strcpy(s,"a汉");
    i=0;
    while (1) {
        if (0==s[i]) break;
        sprintf(hs+i*2,"%02X",(unsigned char)s[i]);
        i++;
    }
    setlocale(LC_ALL,"chs");
    printf("s=%s,hs=%s\n",s,hs);
// 十六进制字符串转成汉字（GBK）及字符(ASC)
    strcpy(hs,"61BABA");
    i=0;
    while (1) {
        if (1!=sscanf(hs+i*2,"%2x",&v)) break;
        s[i]=(char)v;
        i++;
    }
    s[i]=0;
    printf("hs=%s,s=%s\n",hs,s);

    return 0;

}
//i=1024,bs=00000000000000000000010000000000
//i=1024,hs=00000400
//hs=00000400,i=1024
//bs=00000000000000000000010000000000,hs=00000400
//bs=00000000000000000000010000000000,i=1024
//hs=00000400,bs=00000000000000000000010000000000
//s=a汉,hs=61BABA
//hs=61BABA,s=a汉

[智者知已应修善业]

如果不调用现成函数要自己写的话就要写函数式的，本示例适用任意进制。 十六进制的话：fa += x * 乘方(16, c++)；

[Big_Data_1203]

多谢，楼客们！！！

[源代码大师]

C和C++完整教程:https://blog.csdn.net/it_xiangqiang/category_10581430.html C和C++算法完整教程:https://blog.csdn.net/it_xiangqiang/category_10768339.html