#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SKIP_TABLE_SIZE 256
#define STRING_LENGTH 80

void table(int*, char*);  // 建立前進表
int indexOf(int*, int, char*, char*); // 搜尋關鍵字
void subString(char*, char*, int, int); // 取出子字串

int main(void) {
int skip[SKIP_TABLE_SIZE];
char input[STRING_LENGTH];
char key[STRING_LENGTH];
char sub[STRING_LENGTH] = {'\0'};
printf("字串：");
gets(input);
printf("關鍵字：");
gets(key);
table(skip, key);
int m = strlen(input); // 計算字串長度
    int n = strlen(key);
int p = indexOf(skip, n - 1, input, key);
while(p != -1) {
subString(input, sub, p, m);
printf("%s\n", sub);
p = indexOf(skip, p + n + 1, input, key);
}
return 0;
}
void table(int* skip, char *key) {
int n = strlen(key);
int k;
for(k = 0; k < SKIP_TABLE_SIZE; k++) {
skip[k] = n;
}
for(k = 0; k < n - 1; k++) {
skip[key[k]] = n - k - 1;
}
}
int indexOf(int* skip, int from, char* str, char* key) {
char sub[STRING_LENGTH] = {'\0'};
int strLen = strlen(str);
int keyLen = strlen(key);
int index = from;
while(index < strLen) {
subString(str, sub, index - keyLen + 1, index);
if(!strcmp(sub, key)) { // 比較兩字串是否相同
           return index - keyLen + 1;
}
index += skip[str[index]];
}
return -1;
}
void subString(char *text, char* sub, int s, int e) {
int i, j;
for(i = s, j = 0; i <= e; i++, j++) {
sub[j] = text[i];
}
sub[j] = '\0';
}