bin_to_dec.cpp

可转大量超长二进制为十进制

#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include <time.h>

using namespace std;

//-----------------------------------------

void add(char a[],char b[],char c[]);
void clear(char result[]);
void input();
int i,j;
 
int main(){
    char decimal[20];
    char pow[64][20];
	input();

   //initialization	
	for(i=0;i<64;i++)
		for(j=0;j<20;j++){
			decimal[j]='0';
			pow[i][j]='0';
		}

	pow[0][0]='1';
	for(i=1;i<64;i++)
	    add(pow[i-1],pow[i-1],pow[i]);  //get the 1! 2!......64!,store them in pow[64][]

	clock_t t=clock();
	//if you want to test the sample binary data in our textbook,use "test.txt" instead
	ifstream in("change.in.txt");  
	string s;
	bool flag=true;
	for (;getline(in,s);){
		if(s=="-1") break;
        
		//change into the decimal
		int k=0; 
	    for(int i=s.length()-1;i>=0;i--,k++)
			if(s.at(i)=='1') add(decimal,pow[k],decimal);

	    //output the decimal
        for(j=19;j>=0;j--)
	    	if( (decimal[j]=='0') && flag) continue;
	    	else {	cout<<decimal[j];	flag=false;}
		if(flag) cout<<'0';
		cout<<"\n";

		clear(decimal);
		flag=true;
	}	
	cout<<"\nUsing "<<(clock()-t)/CLK_TCK<<" seconds\n";

}//end of main

/*  char a[]+ char b[]=char c[] */
void add(char a[],char b[],char c[]){
	int digit=0,carry=0,bitsum=0;
	while(digit<20){
		bitsum=a[digit]+b[digit]-96+carry; 
		if(bitsum>9) carry=1;
		else carry=0;
		c[digit]=bitsum%10+48;
		digit++;
	}
}

/*clear the decimal[]*/
void clear(char result[]){
	for(int k=0;k<20;k++)
		result[k]='0';
}

void input(){
	ofstream out("change.in.txt");
	for(i=0;i<3000;i++){
		int digits=rand()%64+1;
		for(j=0;j<digits;j++)
		out<<rand()%2;
		out<<endl;
	}
	out<<"-1";
}