字符串匹配 - KMP算法

#include<bits/stdc++.h>
using namespace std;
int *getNext(string p)
{
    int l = p.length(), k = -1, i = 0;
    int *next = new int[l];
    next[0] = -1;
    while(i < l - 1)
    {
        while(k >= 0 && p[k] != p[i])
            k = next[k];
        i++;
        k++;
        if(p[i] == p[k])
            next[i] = next[k];
        else
            next[i] = k;
    }
    return next;
}
int KMPMatching(int *next, string p, string r)
{
    //在 p 中寻找 r 
    int i = 0, j = 0;   //i指向p，j指向r 
    int pl = p.length(), rl = r.length();
    if(pl < rl)
        return -1;
    while(i < pl && j < rl)
    {
        if(j == -1 || p[i] == r[j])
            i++, j++;
        else
            j = next[j];
    }
    if(j >= rl) //说明r被扫描完了，即找到匹配的了 
        return (i - rl);
    else
        return -1;
}
int main()
{
    string p = "abcdaabcab";
    string r = "daa";
    int *next = getNext(p);
    for(int i = 0; i < p.length(); i++)
        cout << next[i] << " ";
    cout << endl; 
    cout << KMPMatching(next, p, r);
    return 0;
}