Question

我有 char * source ，我希望从中获取提取，我知道它是从符号“abc”开始，并在源结束时结束。使用 strstr ，我可以得到更好的，但不是位置，没有位置，我不知道子串的长度。如何在纯C中获取子字符串的索引？

Answer 1

使用指针减法。

char *str = "sdfadabcGGGGGGGGG";
char *result = strstr(str, "abc");
int position = result - str;
int substringLength = strlen(str) - position;

Answer 2

newptr - source会给你抵消。

Answer 3

char *source = "XXXXabcYYYY";
char *dest = strstr(source, "abc");
int pos;

pos = dest - source;

Answer 4

如果你有指向子串的第一个字符的指针，并且子字符串在源字符串的末尾结束，那么：

strlen(substring)会给你它的长度。
substring - source会为您提供开始索引。

Answer 5

这是带有偏移功能的strpos函数的C版本......

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int strpos(char *haystack, char *needle, int offset);
int main()
{
    char *p = "Hello there all y'al, hope that you are all well";
    int pos = strpos(p, "all", 0);
    printf("First all at : %d\n", pos);
    pos = strpos(p, "all", 10);
    printf("Second all at : %d\n", pos);
}


int strpos(char *hay, char *needle, int offset)
{
   char haystack[strlen(hay)];
   strncpy(haystack, hay+offset, strlen(hay)-offset);
   char *p = strstr(haystack, needle);
   if (p)
      return p - haystack+offset;
   return -1;
}

Answer 6

正式其他人是正确的 - substring - source确实是起始指数。但你不需要它：你会用它作为source的索引。因此，编译器会将source + (substring - source)计算为新地址 - 但对于几乎所有用例，只需substring即可。

只是提示优化和简化。

Answer 7

通过开始和结束单词从字符串中删除单词的功能

    string search_string = "check_this_test"; // The string you want to get the substring
    string from_string = "check";             // The word/string you want to start
    string to_string = "test";                // The word/string you want to stop

    string result = search_string;            // Sets the result to the search_string (if from and to word not in search_string)
    int from_match = search_string.IndexOf(from_string) + from_string.Length; // Get position of start word
    int to_match = search_string.IndexOf(to_string);                          // Get position of stop word
    if (from_match > -1 && to_match > -1)                                     // Check if start and stop word in search_string
    {
        result = search_string.Substring(from_match, to_match - from_match);  // Cuts the word between out of the serach_string
    }

获取子字符串的索引

7 个答案: