the c programing language 练习1-21 将空格字符替换为最少数量的制表符和空格

/*
* K&R2 1-21
* Author: Donmmi
* Email:teddy_liu@live.com
 */

#include <stdio.h>

/* 4 spaces to a tab */
#define NTAB    4

int main(void) {
/*
* len is the nums of input charactor
* if (c == ' ' && len % NTAB == 0) translate the space(s) to tab
*/
int     c, len, nspace, flag;

len = nspace = flag = 0;
while ((c = getchar()) != EOF) {
++len;
if (c == ' ') {
if (len % NTAB == 0) { /* space(s) translate to tab */
if (flag == 0)
putchar('\t');
flag = 1;
nspace = 0;
} else
++nspace;
} else {
/*
* If the next charactor is not space and can't translate to tab
* then output saved space and the charactor
*/
while (nspace) {
putchar(' ');
--nspace;
}
putchar(c);
if (c == '\n')
len = 0;
flag = 0;
}
}

return 0;
}