Hello guys,
As a beginner i have some problems with understanding k&r exercises. i came across the exercise: Write a program to remove all trailing blanks and tabs from each line of input, and to delete entirely blank lines.
What is a trailing blank? when i run the code and put some spaces and tabs in the input, nothing seems changed in the output. there's written somewhere: advance(head)==tail, how is this case possible? if i put "space" 3 times, head=3 and then if i put some letters like"abc", tail=3 and blank[0], blank[1], blank[2] will be printed which are "spaces". How is this removing? the same goes if i put spaces after the letters. The soluton to this which i found is here:
Code:#include <stdio.h>#include <stdlib.h> #define MAXQUEUE 1001 int advance(int pointer) { if (pointer < MAXQUEUE - 1) return pointer + 1; else return 0; } int main(void) { char blank[MAXQUEUE]; int head, tail; int nonspace; int retval; int c; retval = nonspace = head = tail = 0; while ((c = getchar()) != EOF) { if (c == '\n') { head = tail = 0; if (nonspace) putchar('\n'); nonspace = 0; } else if (c == ' ' || c == '\t') { if (advance(head) == tail) { putchar(blank[tail]); tail = advance(tail); nonspace = 1; retval = EXIT_FAILURE; } blank[head] = c; head = advance(head); } else { while (head != tail) { putchar(blank[tail]); tail = advance(tail); } putchar(c); nonspace = 1; } } return retval; }
