Q5.2 Print the binary representation

原创于 2015-01-21 20:58:15 发布 · 383 阅读

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本文介绍了一种将0到1之间的实数转换为二进制表示的方法，并提供了一个C++实现示例。该方法通过不断将输入数值乘以2并判断整数部分来生成二进制小数位。

Q:Given a real number between 0 and 1 (eg.,0.72) that is passed in as a string, print the binary representation.If the number can not be represented accurately in binary with 32 characters, print “ERROR”.

A:将num的二进制表示逐位左移，每次将最左一位保存到结果res中。

我们知道，num乘以2，等同于num<<1. 如果乘以2之后，num >= 1, 则res += "1", 否则 res += "0".

#include <iostream>
#include <string>
using namespace std;

string print_binary(double n) {
	if (n >= 1 || n <= 0) return "ERROR";
	string res = ".";
	while (n > 0) {
		if (res.size() >= 32) {
			return "ERROR";
		}
		double tmp = n*2;
		if (tmp >= 1) {
			res += "1";
			tmp = tmp - 1;
		} else {
			res += "0";
		}
		n = tmp;
	}
	return res;
}


int main(){
//    double n = 0.72;
	double n = 0.625;
    cout<<print_binary(n)<<endl;
    return 0;
}