The C Programming Language, 2nd Edition, by Kernighan and Ritchie
Exercise 1.09 on page 20
Write a program to copy its input to its output, replacing each string of one or more blanks by a single blank.
Solution by Dabeau
#include <stdio.h> main() { char c; char prev_c; /* previous character */ prev_c = 0; while ((c = getchar()) != EOF) /* output c if it's not a blank OR if the previous c is not a blank */ if (c != ' ' || prev_c != ' ') { putchar(c); prev_c = c; } }
Solution by Richard Heathfield
#include <stdio.h> int main(void) { int c; int inspace; inspace = 0; while((c = getchar()) != EOF) { if(c == ' ') { if(inspace == 0) { inspace = 1; putchar(c); } } /* We haven't met 'else' yet, so we have to be a little clumsy */ if(c != ' ') { inspace = 0; putchar(c); } } return 0; }
Solution by Chris Sidi
instead of having an "inspace" boolean, you can keep track of the previous character and see if both the current character and previous character are spaces:
#include <stdio.h> /* count lines in input */ int main() { int c, pc; /* c = character, pc = previous character */ /* set pc to a value that wouldn't match any character, in case this program is ever modified to get rid of multiples of other characters */ pc = EOF; while ((c = getchar()) != EOF) { if (c == ' ') if (pc != ' ') /* or if (pc != c) */ putchar(c); /* We haven't met 'else' yet, so we have to be a little clumsy */ if (c != ' ') putchar(c); pc = c; } return 0; }
Solution by Stig Brautaset
I am hiding behind the fact that break is mentioned
in the introduction!
#include <stdio.h> int main(void) { int c; while ((c = getchar()) != EOF) { if (c == ' ') { putchar(c); while((c = getchar()) == ' ' && c != EOF) ; } if (c == EOF) break; /* the break keyword is mentioned * in the introduction... * */ putchar(c); } return 0; }
Solution by Anthony Walters
Here's another solution from Anthony, nut after posting it, I noticed that it looks suspiciously like Stig's solution above!
#include <stdio.h> main() { int inputchar; while((inputchar = getchar()) != EOF) { if(inputchar == ' ') { putchar(inputchar); while((inputchar = getchar()) == ' ') { /* do nothing */ } } if(inputchar != EOF) putchar(inputchar); } }
Solution by OneSadCow
Here is another solution, which is slightly more compact than any of the solutions presented here.
#include <stdio.h> main(){ int c, d; d = EOF; while ((c = getchar()) != EOF){ if (!((d == ' ') && (c == ' '))) putchar(c); d = c; } }
Solution by Platwna
Here is my solution (enjoy!):
#include <stdio.h> void main() { int c; int kena; kena = 0; while ((c = getchar()) != EOF) { if (c == ' ') { ++kena; if (kena < 2) { putchar(c); } } if (c != ' ') { kena = 0; putchar(c); } } }
Solution by pezcore
This is my solution. It was designed not to use logical operators or breaks statements, as they have not been introduced in K&R before example 1.9. Also, it only uses one variable and does not require the use of a "last char" or place holder variable . The main loop executes as follows: read a single char from input and immediately put it to output, regardless of what it is. Then, if that char was a space, continue to read more chars (thus removing them from the input buffer) until it is not a space, and put that char on the output too.
#include <stdio.h> main(){ char c; while((c = getchar()) != EOF){ putchar(c); if (c == 0x20){ while ((c=getchar()) == 0x20); putchar(c); } } }
Solution by Indianlamp
Here is my solution: The first "if" condition checks and prints the character if it's not a space, the second "if" condition prints the first space, after that, if the "while loop" encounters a space, it keeps advancing the to next character, the third "if" condition prints the non-space character advanced to in the second "while loop".
#include<stdio.h> int main() { int c; while((c = getchar()) != EOF) { if (c != ' '){ putchar(c); } if (c == ' '){ putchar(c); while (c == ' '){ c = getchar(); if (c != ' '){ putchar(c); } } } } return 0; }
Solution by Amarakala
Try this
int main(int argc, char** argv) { int c; int prevchar; while((c = getchar()) != EOF) { if(c != prevchar || prevchar != ' ') putchar(c); prevchar = c; } }
Solution by Lvictor
And here is another solution:
#include <stdio.h> int main(){ int c; while((c = getchar()) != EOF){ if(c == ' '){ while((c = getchar()) == ' ') ; putchar(' '); } putchar(c); } }
Solution by Vijaykartha
Here's another solution:
#include <stdio.h> int main() { int c; while ((c=getchar())!=EOF) //This keeps getting characters and checking if it is End of File { putchar(c); //This outputs each character and if it is a blank, outputs it once if (c == ' ') //If the character is a blank, then it goes into a while loop till the next non-blank character { while (c == ' ') //This while loop keeps getting characters and checks if the next character is still blank c=getchar(); //This is part of while loop that keeps getting blank characters without outputting it. putchar(c); //This is outside of the while loop and if a non-blank character is encountered, it is outputted because the outer while loop will get the next character. So, we don't want to missout on a non-blank character. } } }
Solution by Ada123
This is another bad approach from me:
#include <stdio.h> int main() { int c, s = 0; while ( (c = getchar() ) != EOF ) { if (c == ' ') { ++s; } if(c == ' ') { while (s > 1) { printf("\b"); s--; } } else { printf("%c ", c); } } }
Solution by sl4y3r 0wn3r
/* Exercise 1-9. Write a program to copy its input to its output, replacing each string of one or more blanks by a single blank. */ #include <stdio.h> int main(void) { int c = EOF; while ((c = getchar()) != EOF) { if (c == ' ' || c == '\t') { while ((c = getchar()) == ' ' || c == '\t') ; putchar(' '); } putchar(c); } return 0; }
Solution by User:_Kessinger
#include<stdio.h> void main(){ int c,blank=0; while((c = getchar()) != EOF){ // Input character if(c != ' '){ // if char not blank putchar(c); // output char blank = 0; // reset blank count } if(c==' ' && blank<1){ // if char is blank putchar(c); // output blank (only allowed once) blank++; // increment blank } if(c == '\n') // reset blank on newline blank = 0; } }
Solution by Vastousen
Another quick solution
#include <stdio.h> int main() { int c; c=getchar(); while(c != EOF) { printf("%c", c); while (c == ' ') { c=getchar(); if (c != ' ') { printf("%c", c); } } c=getchar(); } }
Solution by Mark Lam
Quick update to the first solution by me - adding a line to show the extra spaces actually removed:
#include <stdio.h> int main(void) { int c; int ns; ns = 0; while ((c = getchar()) != EOF) { if (c == ' ') { if (ns == 0) { ns = 1; putchar(c); } } if (c != ' ') { ns = 0; putchar(c); } } printf("%d\n", c); return 0; }
Solution by Dave
My version:
include <stdio.h> int main() { char c; int blanks; while( (( c=getchar())!=EOF) && !(blanks==2) ) { if(c == ' ') { blanks++; printf("\nBlank detected, amount of blanks: %d\n", blanks); } else { putchar(c); } } return 0; }
Solution by guzmalalo
Only IF and !=
#include <stdio.h> #define SPACE ' ' int main () { int c; int nb = 0; while((c = getchar()) != EOF){ //if (c == SPACE) // (optional), you can assume c is already a blank and increment nb ++nb; if (c != SPACE) nb = 0; if(nb < 2) putchar(c); } return 0; }
