问题
I'm doing an exercise in C but I have a problem when at the and I want to repeat the cicle (do while), infact if I type 1 the programme starts again by the top, but it doesn't stop at the gets(testo); . I tried plenty of ways to solve the bug without a solution, can anyone help me?
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
main(){
int cch, cw, i, j, w, ord, f; //counter and index
char testo[80];
char alfa[50][25];
char swap[25];
do{
cch=0;
cw=0;
j=0;
w=0;
f=0;
for(i=0;i<80;i++){
testo[i]='\0';
}
printf("Write the text:\n");
gets(testo);
//initialization 2d array
for(i=0;i<50;i++){
for(j=0;j<25;j++){
alfa[i][j]='\0';
}
}
j=0;
//Count word and characters
if(testo[0]!='\0'){
cw=1;
for(i=0;testo[i]!='\0';i++){
cch++;
if(testo[i]==' '){
cw++;
j++;
}
}
}
if(cch==j){
printf("You haven't written any word\n\n");
}
else{
//Don't count double space
for(i=0;i<cch;i++){
if(testo[i]==' ' && testo[i+1]==' '){
cw--;
}
}
//Don't count as word if the text start with a space
if(testo[0]==' '){
cw--;
w--;
}
printf("\nThe text is composed by %d characters\n", cch);
printf("The text is composed by %d words\n", cw);
if(cw>0){
printf("\nUsed words:\n");
for(j=0;j<cch;j++){
if(testo[j]==' ' && testo[j+1]==' '){
//nothing to do
}
else{
if(testo[j]!=' '){
alfa[w][f]=testo[j];
f++;
}
else if(testo[j]=='\0'){
alfa[w][f]='\0';
f=0;
w=0;
}
else{
alfa[w][f]='\0';
w++;
f=0;
}
}
}
for(i=0;i<cw;i++){
printf("%d> %s\n", i+1, &alfa[i]);
}
//order
f=1;
printf("\nWords used in alphabetical order:\n");
while(f==1){
f=0;
for(i=0;i<cw-1;i++){
ord=strcmp(alfa[i],alfa[i+1]);
if(ord>0){
strcpy(swap,alfa[i]);
strcpy(alfa[i],alfa[i+1]);
strcpy(alfa[i+1],swap);
f=1;
}
}
}
for(i=0;i<cw;i++){
printf("%d> %s\n", i+1, alfa[i]);
}
}
}
printf("\nDo you want write another text? (1=yes) -> ");
scanf("%d", &j);
}while(j==1);
}
I know that isn't very optimized as code at the moment and has other errors, but I'm having problem on this.
Thank you.
PS: The code is tested on OpenVMS
回答1:
Your first and most obvious problem is with the left over newline. When you use scanf() here:
printf("\nDo you want write another text? (1=yes) -> ");
scanf("%d", &j);
}
and you use the %d format specificer, the function is looking for a number, when you enter a number really you're entering a number and a newline character
> 1<enter key> // which means on stdin you're getting '1''\n'
scanf() only picks up the 1 and leaves the newline which your gets() function then picks up, so it looks like it's skipping the input. All you need to do is consume that newline character, one quick fix would be to consume it with getchar():
printf("\nDo you want write another text? (1=yes) -> ");
scanf("%d", &j);
getchar();
}
Now your program works as you'd expect.
Other issues of note:
- Your main should really be returning an
inttype, even if it's just areturn 0 - You shouldn't be using
gets(), even then man page forgets()says Never use gets(). That's usually a good indication not to. ;) So replace that line withfgets(testo, sizeof(testo), stdin); - You missed a performance specificer here:
printf("\nThe text is composed by % characters\n", cch);so you're getting garbage output, that should have been%d
回答2:
It's because the scanf call at the end of the loop doesn't read the newline. Instead this newline is read by your gets call.
A simple solution is to add a space to the end of the scanf format string, like so:
scanf("%d ", &j);
This will make scanf skip trailing whitespace in the input.
Another solution is to put an extra fgets after the scanf, but then don't add the extra space in the format string:
scanf("%d", &j);
fgets(testo, sizeof(testo), stdin);
Or use fgets to get the line, and then use sscanf to extract the answer:
fgets(testo, sizeof(testo), stdin);
sscanf(testo, "%d", &j);
回答3:
Or you can try using the function flushall() just before gets()
来源：https://stackoverflow.com/questions/15340343/strings-gets-and-do-while