C while 循环额外迭代

Question

我正在尝试 scanf 函数的输入验证。我已经修复了输入以忽略空格(“%c....”)。

有人能看出我做错了什么吗？

#include <stdio.h>
#include <stdlib.h>

int main() {

  char c1, c2, c3;
  int k, done = 0;
  float x;
  double y;

  do {
    printf("\n%s\n%s\n%s\n%s", "Input the following: three characters,", " an int,", " a float,", " and a double: \n");
    if(scanf(" %c%c%c%d%f%lf", &c1, &c2, &c3, &k, &x, &y) == 6){
      printf("\nHere is the data that you typed in: \n");
      printf("%3c%3c%3c%5d%17e%17e\n\n", c1, c2, c3, k, x, y);
      done = 1;
    } else {
      printf("Invalid input!");
    }
  } while (done != 0);

  return EXIT_SUCCESS;
}

Answer 1

首先，变量done未初始化并且具有不确定的值

int k, done;
//...
while(done != 1){

您必须初始化它，例如

int k, done = 0;

但是最好写一个更合适的循环。也就是说，最好使用 do-while 循环来代替 while 循环。例如

int done = 0;
//...

do
{
    printf("\n%s\n%s\n%s\n%s", "Input the following: three characters,", " an int,", " a float,", " and a double: \n");
    if(scanf(" %c%c%c%d%f%lf", &c1, &c2, &c3, &k, &x, &y) == 6){
      printf("\nHere is the data that you typed in: \n");
      printf("%3c%3c%3c%5d%17e%17e\n\n", c1, c2, c3, k, x, y);
      done = 1;
    } else {
      printf("Invalid input!");
    }
} while ( done != 1 );

其次，在 scanf 调用中，您应该为格式说明符指定 balnks %c

例如

    if(scanf(" %c %c %c%d%f%lf", &c1, &c2, &c3, &k, &x, &y) == 6){