#include <iostream>
using std::cout;
using std::endl;
using std::string;
string toBinary(int n)
    string r;
    while (n != 0){
        r += ( n % 2 == 0 ? "0" : "1" );
        n /= 2;
    return r;
int main() {
    int number = 15;
    cout << "decimal: " << number << endl;
    cout << "binary : " << toBinary(number) << endl;
    return EXIT_SUCCESS;
decimal: 15
binary : 1111
使用 std::bitset 类在 C++ 中把十进制数转换为二进制数
另外，我们也可以直接使用 STL 库中的 bitset 类。bitset 表示一个固定大小的 N 位序列，它提供了多种内置方法来有效地操作二进制数据。下面的例子显示了通过传递 string 值和 int 值来构建 bitset 对象。
#include <iostream>
#include <bitset>
using std::cout; using std::endl;
using std::string; using std::bitset;
string toBinary(int n)
    string r;
    while (n != 0){
        r += ( n % 2 == 0 ? "0" : "1" );
        n /= 2;
    return r;
int main() {
    int number = 15;
    bitset<32> bs1(toBinary(number));
    cout << "binary:  " << bs1 << endl;
    bitset<32> bs2(number);
    cout << "binary:  " << bs2 << endl;
    return EXIT_SUCCESS;
binary:  00000000000000000000000000001111
binary:  00000000000000000000000000001111
请注意，在前面的代码中，我们在 bitset 声明中指定了 32 位的分配。大家可以指定不同的位数，以更好地满足自己的需求。下面的代码段中演示了多种方案。
#include <iostream>
#include <bitset>
using std::cout; using std::endl;
using std::string; using std::bitset;
int main() {
    int number = 15;
    bitset<32> bs1(number);
    cout << "binary:  " << bs1 << endl;
    bitset<16> bs2(number);
    cout << "binary:  " << bs2 << endl;
    bitset<8> bs3(number);
    cout << "binary:  " << bs3 << endl;
    bitset<5> bs4(number);
    cout << "binary:  " << bs4 << endl;
    cout << endl;
    return EXIT_SUCCESS;
binary:  00000000000000000000000000001111
binary:  0000000000001111
binary:  00001111
binary:  01111
bitset 类有几个有用的方法对其内容进行操作。这些方法可以用来反转集合的所有位（flip 函数）或 reset/set 序列中指定的位。还支持核心的二进制运算，如 AND、OR、XOR、NOT 和 SHIFT。我们在下面的例子中展示了其中的几个，但你可以看到 bitset 类的完整手册这里。
#include <iostream>
#include <bitset>
using std::cout; using std::endl;
using std::string; using std::bitset;
int main() {
    int number = 15;
    bitset<32> bs(number);
    cout << "binary : " << bs << endl;
    cout << "flipped: " << bs.flip() << endl;
    cout << "shift>4: " << (bs>>=6) << endl;
    cout << "shift<5: " << (bs<<2) << endl;
    cout << "reset  : " << bs.reset() << endl;
    cout << "set    : " << bs.set(16) << endl;
    return EXIT_SUCCESS;
binary : 00000000000000000000000000001111
flipped: 11111111111111111111111111110000
shift>4: 00000011111111111111111111111111
shift<5: 00001111111111111111111111111100
reset  : 00000000000000000000000000000000
set    : 00000000000000010000000000000000
    
Author: Jinku Hu
                
Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.
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