字符串匹配KMP算法

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package Str.pipei;import java.util.Calendar;public class String_Kmp {    public String_Kmp() {        // TODO Auto-generated constructor stub    }    public static int[] getNext(String ps) {        char[] p = ps.toCharArray();        int[] next = new int[p.length];        next[0] = -1;        int j = 0;        int k = -1;        while (j < p.length - 1) {            if (k == -1 || p[j] == p[k]) {                next[++j] = ++k;            } else {                k = next[k];            }        }        return next;    }    /**     *      * 暴力破解法     *      * @param srcText     *            主串     *      * @param ps     *            模式串     *      * @return 如果找到，返回在主串中第一个字符出现的下标，否则为-1     *      */    public static int bf(String srcText, String ps) {        char[] t = srcText.toCharArray();        char[] p = ps.toCharArray();        int i = 0; // 主串的位置        int j = 0; // 模式串的位置        // 匹配上的结果是j等于p.length        while (i < (t.length) && j < p.length) {            if (t[i] == p[j]) { // 当两个字符相同，就比较下一个                i++;                j++;            } else {                i = i - j + 1; // 一旦不匹配，i后退                j = 0; // j归0            }        }        if (j == p.length) {            return i - j;        } else {            return -1;        }    }    public static int KMP(String ts, String ps) {        char[] t = ts.toCharArray();        char[] p = ps.toCharArray();        int i = 0; // 主串的位置        int j = 0; // 模式串的位置        int[] next = getNext(ps);        while (i < t.length && j < p.length) {            if (j == -1 || t[i] == p[j]) { // 当j为-1时，要移动的是i，当然j也要归0                i++;                j++;            } else {                // i不需要回溯了                // i = i - j + 1;                j = next[j]; // j回到指定位置            }        }        if (j == p.length) {            return i - j;        } else {            return -1;        }    }    public static void main(String[] args) {        // TODO Auto-generated method stub        String_Kmp str = new String_Kmp();        System.out.println(Calendar.getInstance().getTime());        System.out.println(str.KMP("lsjflSJlasjflkjsalkjfa;lkjdflkajsldfj;assaflk;jdflkjas;ld"                + "dlfkjsalkdjflska;jfksa;lkjfslak;jf;lsajfl;sakjflska;jlkfjdaljdkal;dkfja;skjdf"                + "sadlkfjsladjkfljdflkjwoeijfwlekjwlkejrow"                + "sldkfjlsakjflkjdflkasj;ldfkjasl;kfjsa;ldkfjal;sdfjl;askjflkajfklja;sfjkjwekjfsa;ld"                + "Flsadkjflksaj;flkjd;lkjakdfjalskjdf" + "sadklfjslakjlk;dfjlaskjdflkjasd"                + "saflksajflkjsa;lfkjasdfl;askjflk;asjflkjaslfkj;asldkfj;lsa"                + "lfjsdlfkja;lkjfljeoijlskjf2465154651465s4f3as24f654fsad5f"                + "asfsafasfasfsfsafdfsdfdfasLSJSJ;LSAJFLSJFLSJL;KJLSALJ  SLDFJ"                + "LSJFLKJSLDFJLJALKJFL;SAJLJsljflsjdfljsldj" + "sdjflkjsdlkjfljksd" + "sdl;kjflsjdf;jakfdlfj"                + "sdkjflksjdlkfjsla;jfkjsalkjdflkajs;kfjoweijofiejroijofieuoifjweoiruoi3u4o3i2j4l2k3j"                + "sadfasfsadfsafasdfajajslkdlk", "jfkjsalkjdflkajs;"));        System.out.println(Calendar.getInstance().getTime());        System.out.println(Calendar.getInstance().getTime());        System.out.println(str.bf("lsjflSJlasjflkjsalkjfa;lkjdflkajsldfj;assaflk;jdflkjas;ld"                + "dlfkjsalkdjflska;jfksa;lkjfslak;jf;lsajfl;sakjflska;jlkfjdaljdkal;dkfja;skjdf"                + "sadlkfjsladjkfljdflkjwoeijfwlekjwlkejrow"                + "sldkfjlsakjflkjdflkasj;ldfkjasl;kfjsa;ldkfjal;sdfjl;askjflkajfklja;sfjkjwekjfsa;ld"                + "Flsadkjflksaj;flkjd;lkjakdfjalskjdf" + "sadklfjslakjlk;dfjlaskjdflkjasd"                + "saflksajflkjsa;lfkjasdfl;askjflk;asjflkjaslfkj;asldkfj;lsa"                + "lfjsdlfkja;lkjfljeoijlskjf2465154651465s4f3as24f654fsad5f"                + "asfsafasfasfsfsafdfsdfdfasLSJSJ;LSAJFLSJFLSJL;KJLSALJ  SLDFJ"                + "LSJFLKJSLDFJLJALKJFL;SAJLJsljflsjdfljsldj" + "sdjflkjsdlkjfljksd" + "sdl;kjflsjdf;jakfdlfj"                + "sdkjflksjdlkfjsla;jfkjsalkjdflkajs;kfjoweijofiejroijofieuoifjweoiruoi3u4o3i2j4l2k3j"                + "sadfasfsadfsafasdfajajslkdlk", "jfkjsalkjdflkajs;"));        System.out.println(Calendar.getInstance().getTime());    }}
输出结果看到用两种不同算法，暴力遍历以及KMP算法都是可以实现的。但是那么多字符在时间上好像没什么特别的差距。
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