数字字符串上的STRCMP

所以我有3个变量：

char fromAge[4];
char toAge[4];
char age[4];

它们都可以有一个介于18和100之间的数字，包括18和100。 当我给他们下列值时，出于某种原因，以下陈述是错误的：

fromAge[4] = 18;
toAge[4] = 100;
age[4] = 25;
if (strcmp(age, fromAge) >= 0 && strcmp(age, toAge) <= 0)
{
//actions
}

---

年龄是2,5，'\0'

你在检查字符串，这意味着你在按字母顺序检查它，事实上：2在字母表中不在1之前：在ASCII中，2的值是50，而1的值是49，事实上：50不在49之前

因此，使用数字作为字符串总是一个坏主意，只需将它们视为数字，一切都应该很好：

int FromAge;
int ToAge;
...

好运

strcmp通过从左到右比较单个字符来比较字符串，一旦两个字符不同，它就会返回。由于字符“1”小于字符“2”，因此字符串100将被视为小于字符串25

试试这个代码，输入100和25

int main()
{
  char toAge[4] = {0};
  char age[4]={0};
  scanf("%3s", age);
  scanf("%3s", toAge);

  // Using string compare
  if (strcmp(age, toAge) < 0)
    printf("\"%s\" is less than \"%s\"\n", age, toAge);
  else if (strcmp(age, toAge) > 0)
    printf("\"%s\" is greater than \"%s\"\n", age, toAge);
  else
    printf("\"%s\" is equal to \"%s\"\n", age, toAge);

  // Using integer compare
  if (atoi(age) < atoi(toAge))
    printf("%s is less than %s\n", age, toAge);
  else if (atoi(age) > atoi(toAge))
    printf("%s is greater than %s\n", age, toAge);
  else
    printf("%s is equal to %s\n", age, toAge);

  return 0;
}

---

正如您所见，函数atoi可用于获得预期结果。

C中的索引从0开始。所以fromAge[4]并不存在。定义的fromAge[4]仅从fromAge[0]到fromAge[3]等等。这不是为字符数组分配数值的方式。使用atoi

int main()
{
  char toAge[4] = {0};
  char age[4]={0};
  scanf("%3s", age);
  scanf("%3s", toAge);

  // Using string compare
  if (strcmp(age, toAge) < 0)
    printf("\"%s\" is less than \"%s\"\n", age, toAge);
  else if (strcmp(age, toAge) > 0)
    printf("\"%s\" is greater than \"%s\"\n", age, toAge);
  else
    printf("\"%s\" is equal to \"%s\"\n", age, toAge);

  // Using integer compare
  if (atoi(age) < atoi(toAge))
    printf("%s is less than %s\n", age, toAge);
  else if (atoi(age) > atoi(toAge))
    printf("%s is greater than %s\n", age, toAge);
  else
    printf("%s is equal to %s\n", age, toAge);

  return 0;
}

"100" is less than "25"
100 is greater than 25