编辑代码

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

int findstringbyforce(char txt[],char pattern[]){
    int txtlen = strlen(txt);
    int patternlen = strlen(pattern);
    int mindex = -1;

    if(txtlen == 0 || patternlen == 0){
        return mindex;   // 说明没找到，返回下标-1
    }

    for (int i = 0; i<txtlen - patternlen + 1;++i){
        int j = 0;
        for (; j < patternlen;++j){
            if(txt[i + j] != pattern[j]){
                break;
            } 

        }
        if(j == patternlen){
            mindex = i;
            break;
        }
    }

    return mindex;
}

int main () {
    printf("%d\n",findstringbyforce("NOBODY_NOTICED_HIM", ""));
    printf("%d\n",findstringbyforce("NOBODY_NOTICED_HIM", "NOT"));
    printf("%d\n",findstringbyforce("NOBODY_NOTICED_HIM", "BODY"));
    return 0;
}