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