68 lines
1.4 KiB
Text
68 lines
1.4 KiB
Text
/* Paul Lou and Tanner Haldeman */
|
|
/* References: Algorithms (Sedgewick), https://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm */
|
|
|
|
int[] construct_table(string w) {
|
|
var length = length_of_string(w);
|
|
var arr_of_w = array_of_string(w);
|
|
var t = new int[length];
|
|
var curr = 2;
|
|
var next = 0;
|
|
|
|
t[0] = -1;
|
|
t[1] = 0;
|
|
while (curr < length) {
|
|
if (arr_of_w[curr-1] == arr_of_w[next]) {
|
|
t[curr] = next + 1;
|
|
next = next + 1;
|
|
curr = curr + 1;
|
|
}
|
|
else if (next > 0) {
|
|
next = t[next];
|
|
}
|
|
else {
|
|
t[curr] = 0;
|
|
curr = curr + 1;
|
|
}
|
|
}
|
|
|
|
return t;
|
|
}
|
|
|
|
|
|
int kmp(string str, string w) {
|
|
var str_idx = 0;
|
|
var word_idx = 0;
|
|
var word_length = length_of_string(w);
|
|
var word_arr = array_of_string(w);
|
|
var str_arr = array_of_string(str);
|
|
var t = construct_table(w);
|
|
|
|
while (str_idx + word_idx < length_of_string(str)) {
|
|
if (word_arr[word_idx] == str_arr[str_idx + word_idx]) {
|
|
if (word_idx == word_length - 1) {
|
|
return str_idx;
|
|
}
|
|
word_idx = word_idx + 1;
|
|
}
|
|
else {
|
|
if (t[word_idx] > -1) {
|
|
str_idx = str_idx + word_idx - t[word_idx];
|
|
word_idx = t[word_idx];
|
|
}
|
|
else {
|
|
str_idx = str_idx + 1;
|
|
word_idx = 0;
|
|
}
|
|
}
|
|
}
|
|
|
|
return -1;
|
|
}
|
|
|
|
int program(int argc, string[] argv) {
|
|
var str = "abcdabcdabcdcbab";
|
|
var word = "dabcdc";
|
|
|
|
var ret = kmp(str, word);
|
|
return ret;
|
|
}
|