1 /*
2  * 1-21. Write a program entab that replaces strings of blanks by the minimum number of tabs and blanks to achieve the same spacing. Use the same tab stops as for detab. When either a tab or a single blank would suffice to reach a tab stop, which should be given preference?
3  */
4 
5 #include <stdio.h>
6 #define TABSTOP 8
7 
8 main()
9 {
10 	int c, col, spaces;
11 
12 	for (col = 1, spaces = 0; (c = getchar())!=EOF; ++col) {
13 		if (c == ' ') {
14 			if (col%TABSTOP == 0) {
15 				printf ("\t");
16 				spaces = 0;
17 			} else {
18 				++spaces;
19 			}
20 		} else if (c == '\t') {
21 			do {
22 				printf(" ");
23 				++col;
24 			} while (col%TABSTOP != 1);
25 		} else {
26 			for (int i = 0; i < spaces; ++i) {
27 				printf(" ");
28 			}
29 			spaces = 0;
30 			printf("%c", c);
31 			if (c == '\n') {
32 				col = 0;
33 			}
34 		}
35 	}
36 }