C语言把整数转换成二进制字符串

代码正文双击正文可选择全部

1[代码][c]register用在大量循环中才能节省时间，不然很难看出效果

#include <time.h>
#include <stdio.h>
char * itobs(register int n, register char * ps)
{
	register int size = 8 * sizeof(int);
	for (register int i = size - 1; i >= 0; i--, n >>= 1)
		ps[i] = (01 & n) + '0';
	ps[size] = '\0';
	return ps;
}
	
char * getBin(register int num,register char *p) {
	register int w=sizeof(int)*8;
	p[0]='\0';
    for (register int i = w - 1; i >= 0; i--) {
        register _Bool bit = (num >> i) & 1;
	   	push(p,bit ? '1':'0');
		//if(i%8==0)	push(p,' ');//8位空一格
    }
	return p;
}
void push(register char *p,register char c) {
	register int len=strlen(p);
	p[len]=c;
	p[len+1]='\0';
}
	
/*4位一组显示二进制字符串 */
void show_bstr(const register char * str)
{
	register int i = 0;
	while (str[i]){
		putchar(str[i]);
		if (++i % 8 == 0 && str[i])
			putchar(' ');
	}
}
int add(register int i){
	for(register int j=1;j<=1147483646;j++)//2147483647
		i++;
	return i;
}
int main(void)
{
	clock_t start_t, end_t;
	char t[65];
	int i=0;
	
	start_t = clock();
	printf("程序启动，start_t = %ld\n", start_t);
	
	printf("%d\n",'A');
	
	show_bstr(itobs('A',t));
	
	printf("\n");
	
	show_bstr(getBin('A',t));
	
	//i=add(i);
	
	end_t = clock();
	printf("\n大循环结束，end_t = %ld\n", end_t);   
	printf("CPU 占用的总时间：%f秒 %d\n", (double)(end_t - start_t) / CLOCKS_PER_SEC,i);
	
	return 0;
}
/*运行结果
程序启动，start_t = 1369
65
00000000 00000000 00000000 01000001
00000000 00000000 00000000 01000001
大循环结束，end_t = 1425
CPU 占用的总时间：0.000056秒 0
*/

2[代码][c]这里不用register

#include <time.h>
#include <stdio.h>
char * itobs(int n, char * ps)
{
	int size = 8 * sizeof(int);
	for (int i = size - 1; i >= 0; i--, n >>= 1)
		ps[i] = (01 & n) + '0';
	ps[size] = '\0';
	return ps;
}
	
char * getBin(int num,char *p) {
	int w=sizeof(int)*8;
	p[0]='\0';
    for (int i = w - 1; i >= 0; i--) {
        _Bool bit = (num >> i) & 1;
	   	push(p,bit ? '1':'0');
		//if(i%8==0)	push(p,' ');//8位空一格
    }
	return p;
}
void push(char *p,char c) {
	int len=strlen(p);
	p[len]=c;
	p[len+1]='\0';
}
	
/*4位一组显示二进制字符串 */
void show_bstr(const char * str)
{
	int i = 0;
	while (str[i]){
		putchar(str[i]);
		if (++i % 8 == 0 && str[i])
			putchar(' ');
	}
}
int add(int i){
	for(int j=1;j<=1147483646;j++)//2147483647
		i++;
	return i;
}
int main(void)
{
	clock_t start_t, end_t;
	char t[65];
	int i=0;
	
	start_t = clock();
	printf("程序启动，start_t = %ld\n", start_t);
	
	printf("%d\n",'A');
	
	show_bstr(itobs('A',t));
	
	printf("\n");
	
	show_bstr(getBin('A',t));
	
	//i=add(i);
	
	end_t = clock();
	printf("\n大循环结束，end_t = %ld\n", end_t);   
	printf("CPU 占用的总时间：%f秒 %d\n", (double)(end_t - start_t) / CLOCKS_PER_SEC,i);
	
	return 0;
}
/*运行结果
程序启动，start_t = 1358
65
00000000 00000000 00000000 01000001
00000000 00000000 00000000 01000001
大循环结束，end_t = 1415
CPU 占用的总时间：0.000057秒 0
*/