使用C语言解决字符串匹配问题的方法

#include <stdio.h>#include <stdlib.h>#include <string.h>int get_nextval(char *pattern, int next[]){  //get the next value of the pattern   int i = 0, j = -1;  next[0] = -1;  int patlen = strlen(pattern);  while ( i < patlen - 1){    if ( j == -1 || pattern[i] == pattern[j]){      ++i;      ++j;      if (pattern[i] != pattern[j])        next[i] = j;      else        next[i] = next[j];    }    else      j = next[j];    }  return(0);}int kmpindex(char *target, char *pattern, int pos){  int tari = pos, pati = 0;   int tarlen = strlen(target), patlen = strlen(pattern);  int *next = (int *)malloc(patlen * sizeof(int));  get_nextval(pattern, next);  while ( tari < tarlen && pati < patlen ){    if (pati == -1 ||target[tari] == pattern[pati]){      ++tari;      ++pati;      }else{        pati = next[pati];      }  }  if(next != NULL) free(next);next = NULL;if (pati == patlen)  return tari - pati;else  return -1;}int main(){  char target[50], pattern[50];  printf("imput the target:/n" );  scanf("%s",target);  printf("imput the pattern:/n" );  scanf("%s",pattern);  int ans = kmpindex(target,pattern,0);  if (ans == -1)    printf("error/n");  else    printf("index:%d/n",ans);  return 0;}

  #include <stdio.h>   #include <stdlib.h>   #include <string.h>       #define MAX 1001   #define LEN 101       struct str   {     char name[101];   };       int main()   {     struct str strs[MAX];     struct str t[LEN];     int i, n, len, j, k, left, right, count, flag;     char text[LEN], newtext[LEN];         while (scanf("%d", &n) != EOF) {       // 接收数据       getchar();       for (i = 0; i < n; i ++) {         scanf("%s", strs[i].name);       }           // 接收文本串       getchar();       gets(text);       len = strlen(text);           for (i = left = right = 0; i < len; i ++) {         if (text[i] == '[') {           left = i;         } else if (text[i] == ']') {           right = i;           break;         }       }       count = right - left - 1;           if (count <= 0) {  // 没有正则匹配         for (i = j = 0; i < len; i ++) {           if (text[i] != '[' && text[i] != ']') {             newtext[j ++] = text[i];           }         }         newtext[j] = '/0';         for (i = 0; i < n; i ++) {           if (strcasecmp(strs[i].name, newtext) == 0) {             printf("%d %s/n", i + 1, strs[i].name);           }         }       }else { // 需要正则匹配         for (j = 1, k = 0; j <= count; j ++, k ++) { // 构建文本数组           memset(t[k].name, '/0', sizeof(t[k].name));           for (i = 0; i < left; i ++) {             t[k].name[i] = text[i];           }           t[k].name[i] = text[left + j];           strcat(t[k].name, text + right + 1);           }                   // 正则匹配          for (i = 0; i < n; i ++) {           for (j = flag = 0; j < count; j ++) {             if (strcasecmp(strs[i].name, t[j].name) == 0) {               flag = 1;               break;             }           }           if (flag) {             printf("%d %s/n", i + 1, strs[i].name);           }         }       }         }         return 0;   }