【C语言经典算法】将一个整数按二进制输出

---

1、用位运算实现

• 将mask右移

#include <stdio.h>

int main()
{
    
    
	
	const int bits = sizeof(int) * 8;	
	unsigned int mask = 1 << bits - 1;// 0x80000000
	int n;
	printf("Input an integer:");
	scanf("%d", &n);
	for (int i = 0; i < bits; i++)
	{
    
    
		printf("%c", n & mask ? '1' : '0');
		mask>>=1;
	}
	return 0;
}

• 将n左移

#include <stdio.h>

int main()
{
    
    
	
	const int bits = sizeof(int) * 8;	
	unsigned int mask = 1 << bits - 1;// 0x80000000
	int n;
	printf("Input an integer:");
	scanf("%d", &n);
	for (int i = 0; i < bits; i++)
	{
    
    
		printf("%c", n & mask ? '1' : '0');
		n <<= 1;
	}
	return 0;
}

2、用符号位实现

• 当整数为负数时，最高位为1

int main()
{
    
    
	const int bits = sizeof(int) * 8;
	unsigned int mask = 1 << bits - 1;
	int n=0;
	scanf("%d", &n);
	int i;
	printf("Input an integer");
	for (i = 0; i < bits; i++)
	{
    
    		
		printf("%c", n > 0?'0' : '1');
		n <<= 1;
	}

	return 0;
}

#include <stdio.h>

int main()
{
    
    
	const int bits = sizeof(int) * 8;
	unsigned int mask = 1 << bits - 1;
	int n=0;
	printf("Input an integer:");
	scanf("%d", &n);
	int i;
	
	for (i = 0; i < bits; i++)
	{
    
    		
		printf("%d", n < 0);//小于0时，最高位为1，这里是%d
		n <<= 1;
	}

	return 0;
}