我自己的简单解决方案(区分大小写):

uint8_t strContains(char* string, char* toFind)
{
    uint8_t slen = strlen(string);
    uint8_t tFlen = strlen(toFind);
    uint8_t found = 0;

    if( slen >= tFlen )
    {
        for(uint8_t s=0, t=0; s<slen; s++)
        {
            do{

                if( string[s] == toFind[t] )
                {
                    if( ++found == tFlen ) return 1;
                    s++;
                    t++;
                }
                else { s -= found; found=0; t=0; }

              }while(found);
        }
        return 0;
    }
    else return -1;
}

结果

strContains("this is my sample example", "th") // 1
strContains("this is my sample example", "sample") // 1
strContains("this is my sample example", "xam") // 1
strContains("this is my sample example", "ple") // 1
strContains("this is my sample example", "ssample") // 0
strContains("this is my sample example", "samplee") // 0
strContains("this is my sample example", "") // 0
strContains("str", "longer sentence") // -1
strContains("ssssssample", "sample") // 1
strContains("sample", "sample") // 1

在ATmega328P上测试(avr8-gnu-toolchain-3.5.4.1709);)

#include <stdio.h>
#include <string.h>

int findSubstr(char *inpText, char *pattern);
int main()
{
    printf("Hello, World!\n");
    char *Text = "This is my sample program";
    char *pattern = "sample";
    int pos = findSubstr(Text, pattern);
    if (pos > -1) {
        printf("Found the substring at position %d \n", pos);
    }
    else
        printf("No match found \n");

    return 0;
}

int findSubstr(char *inpText, char *pattern) {
    int inplen = strlen(inpText);
    while (inpText != NULL) {

        char *remTxt = inpText;
        char *remPat = pattern;

        if (strlen(remTxt) < strlen(remPat)) {
            /* printf ("length issue remTxt %s \nremPath %s \n", remTxt, remPat); */
            return -1;
        }

        while (*remTxt++ == *remPat++) {
            printf("remTxt %s \nremPath %s \n", remTxt, remPat);
            if (*remPat == '\0') {
                printf ("match found \n");
                return inplen - strlen(inpText+1);
            }
            if (remTxt == NULL) {
                return -1;
            }
        }
        remPat = pattern;

        inpText++;
    }
}

使用C -没有内置函数

String_contains()完成所有繁重的工作，并返回基于1的索引。其余是驱动程序和辅助程序代码。

指定指向主字符串和子字符串的指针，匹配时增加子字符串指针，当子字符串指针等于子字符串长度时停止循环。

read_line()—一个额外的代码，用于读取用户输入，而不需要预先定义用户应该提供的输入大小。

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

int string_len(char * string){
  int len = 0;
  while(*string!='\0'){
    len++;
    string++;
  }
  return len;
}

int string_contains(char *string, char *substring){
  int start_index = 0;
  int string_index=0, substring_index=0;
  int substring_len =string_len(substring);
  int s_len = string_len(string);
  while(substring_index<substring_len && string_index<s_len){
    if(*(string+string_index)==*(substring+substring_index)){
      substring_index++;
    }
    string_index++;
    if(substring_index==substring_len){
      return string_index-substring_len+1;
    }
  }

  return 0;

}

#define INPUT_BUFFER 64
char *read_line(){
  int buffer_len = INPUT_BUFFER;
  char *input = malloc(buffer_len*sizeof(char));
  int c, count=0;

  while(1){
    c = getchar();

    if(c==EOF||c=='\n'){
      input[count]='\0';
      return input;
    }else{
      input[count]=c;
      count++;
    }

    if(count==buffer_len){
      buffer_len+=INPUT_BUFFER;
      input = realloc(input, buffer_len*sizeof(char));
    }

  }
}

int main(void) {
  while(1){
    printf("\nEnter the string: ");
    char *string = read_line();
    printf("Enter the sub-string: ");
    char *substring = read_line(); 
    int position = string_contains(string,substring);
    if(position){ 
      printf("Found at position: %d\n", position);
    }else{
      printf("Not Found\n");
    }
  }
  return 0;
}

if (strstr(sent, word) != NULL) {
    /* ... */
}

注意，如果找到单词word, strstr将返回一个指向在sent中单词开头的指针。

我相信我有最简单的答案。在这个程序中不需要string.h库，也不需要stdbol .h库。简单地使用指针和指针算术将帮助您成为一个更好的C程序员。

如果是False，返回0(没有找到子字符串)，如果是True，返回1(是的，在整个字符串“str”中找到了子字符串“sub”):

#include <stdlib.h>

int is_substr(char *str, char *sub)
{
  int num_matches = 0;
  int sub_size = 0;
  // If there are as many matches as there are characters in sub, then a substring exists.
  while (*sub != '\0') {
    sub_size++;
    sub++;
  }

  sub = sub - sub_size;  // Reset pointer to original place.
  while (*str != '\0') {
    while (*sub == *str && *sub != '\0') {
      num_matches++;
      sub++;
      str++;
    }
    if (num_matches == sub_size) {
      return 1;
    }
    num_matches = 0;  // Reset counter to 0 whenever a difference is found. 
    str++;
  }
  return 0;
}

My code to find out if substring is exist in string or not 
// input ( first line -->> string , 2nd lin ->>> no. of queries for substring
following n lines -->> string to check if substring or not..

#include <stdio.h>
int len,len1;
int isSubstring(char *s, char *sub,int i,int j)
{

        int ans =0;
         for(;i<len,j<len1;i++,j++)
        {
                if(s[i] != sub[j])
                {
                    ans =1;
                    break;
                }
        }
        if(j == len1 && ans ==0)
        {
            return 1;
        }
        else if(ans==1)
            return 0;
return 0;
}
int main(){
    char s[100001];
    char sub[100001];
    scanf("%s", &s);// Reading input from STDIN
    int no;
    scanf("%d",&no);
    int i ,j;
    i=0;
    j=0;
    int ans =0;
    len = strlen(s);
    while(no--)
    {
        i=0;
        j=0;
        ans=0;
        scanf("%s",&sub);
        len1=strlen(sub);
        int value;
        for(i=0;i<len;i++)
        {
                if(s[i]==sub[j])
                {
                    value = isSubstring(s,sub,i,j);
                    if(value)
                    {
                        printf("Yes\n");
                        ans = 1;
                        break;
                    }
                }
        }
        if(ans==0)
            printf("No\n");

    }
}