kmp算法

链接kmp算法 

next[i]数组实际上是i之前字符串前缀和后缀的最长的公共串的长度，其中前缀部分和后缀部分不能相交

代码如下：

private int[] kmp_table(String s)
    {
        int[] next = new int[s.length()];

        next[0] = -1;
        int j = 0;

        for (int i = 1; i < s.length(); i++) {
            int k = next[i - 1];
            while (k > -1 && s.charAt(k) != s.charAt(i - 1)) {
                k = next[k];
            }

            next[i] = k + 1;
        }

        return next;
    }

    private int kmp_search(String text, String pattern)
    {
        int[] next = kmp_table(pattern);
        int m = 0, i = 0;

        while (m + i < text.length()) {
            while (pattern.charAt(i) == text.charAt(m + i)) {
                if (++i == pattern.length()) {
                    return m;
                }
            }

            m += i - next[i];
            i = next[i] > -1 ? next[i] : 0;
        }

        return 0;
    }