[draft]字符串匹配 Z_algorithm

来源：互联网发布：王者荣耀自慰软件编辑：程序博客网时间：2024/05/18 00:33

Z algorithm 和字符串匹配的几个算法其实类似，主要利用了pattern的重复信息。

具体思想在这里，这个slides写得非常好懂。

还有个demo也很好。

我实现了一下code(暂时还没去测试是否bugfree)

public class ZAlgo {private int [] z;private char [] text;public ZAlgo() {z = null;text = null;}private int basicPrefixMatch(int index) {int i = 0;while (index < text.length && text[index] == text[i]) {++i;++index;}return i;}//                " a  a  b  c  a  a  b  x  a  a  a  z"//                " 0     2     4     6     8     10  "// wrong answer:   12, 1, 0, 0, 3, 1, 0, 0, 2, 1, 1, 0  // correct answer: 12, 1, 0, 0, 3, 1, 0, 0, 2, 2, 1, 0public void populateZ(String str) {text = str.toCharArray();z = new int[text.length];int l = 0;int r = 0;z[0] = text.length;for (int index = 1; index < text.length; ++index) {if (index > r) {z[index] = basicPrefixMatch(index);System.out.printf("a:index = %d, z[index] = %d\n", index, z[index]);if (z[index] > 0) {l = index;r = index + z[index] - 1;}//print_array('a');}else {if (z[index - l]  < r - index + 1) {z[index] = z[index - l];print_array('b');} else {int i = r + 1;int start = r -index + 1;//System.out.printf("debug:index = %d, i = %d, start = %d\n", index, i, start); // note below: compare text array instead of z value arraywhile (i < text.length && text[i] == text[start]) {++i;++start;}l = index;r = i -1;z[index] = r - l +1;//print_array('c');}}//System.out.printf("index = %d, l=%d, r=%d%n%n", index, l, r);}}public void print_array(char c) {System.out.printf("%c:", c);for (int i = 0; i < z.length; ++i) {System.out.printf("%d, ", z[i]);}System.out.println();}public static void main(String[] args) {// TODO Auto-generated method stubZAlgo zalgo = new ZAlgo();String input = new String("aabcaabxaaaz");zalgo.populateZ(input);zalgo.print_array('z');}}

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