用C反向字符串 [英] Reverse strings in C

问题描述

什么是与以下code中的问题？

What's the problem with the following code?

#define N 30
int main() {
    char str[N], new_str[N];
    int i,len;
    printf("Please enter 20 letters. \n");
    scanf("%s", str);
    len = strlen(str);
    printf("The length of str is  %d ", len);
    for (i=0; i< len; i++)
        new_str[i]=str[len-1-i];
    printf("The result is: %s\n", new_str);
    return 1;
}

我检查下16个字符的字符串每次的程序确定，它上面返回末不确定的字符：

I checked that for every string under 16 characters the program is OK, and above it returns undefined characters at the end:

  Please enter 20 letters.
  1234567891111111

  The result is: 1111111987654321q=V?.

不过，如果我初始化海峡，new_str 以问题就解决了​​。我仍然不知道是什么原因导致的问题。

However, if I initialize str, new_str with "" the problem is solved. I still I wonder what causes the problem.

推荐答案

您需要添加空终止：

new_str[len] = '\0';

否则，是最后一个字符后的垃圾，因此字符串没有结束

otherwise, there is garbage after the last character, so the string is not ending

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