算法之美--3.2.2 MP算法

这块硬骨头，放在这里半年的时间了，一直没有动，今天周末看看，书上把过程写的比较详细，自己基本也看懂了，但是对代码本身的编写还是比较生疏，要经常复习，估计才能看透，后面有看了kmp;这两者之间的关系也是头大。。。

/*!
 * file MP_算法.cpp
 *
 * author ranjiewen
 * date 2017/02/12 15:06
 *
 * 
 */

void preMp(const char *pattern, int m, int mpNext[]) //m为pattern的长度
{
    int i, j;
    i = 0;
    j = mpNext[0] = -1;
    while (i<m)
    {
        while (j>-1&&pattern[i]!=pattern[j]) //
        {
            j = mpNext[j];
        }
        mpNext[++i] = ++j;  //mpNext(j)=f(j-1)+1
    }
}

#include <iostream>
#include <string>
using namespace std;

void MP(string pattern, string target)
{
    int m = pattern.length();
    int n = target.length();
    if (m>n)
    {
        cerr << "Unsuccessful match!" << endl;
        return;
    }
    const char* x = pattern.c_str();
    const char* y = target.c_str();
    int i = 0, j = 0, mpNext[128];  //m+1大小

    preMp(x, m, mpNext);  //mpNext 进行一下轮比较过程中模式P的起始比较位置

    bool flag = false;
    while (i<n)   //i 遍历target字符串
    {
        while (j>-1&&x[j]!=y[i])  //j 匹配模式字符串
        {
            j = mpNext[j];
        }
        j++;
        i++;

        if (j>=m)
        {
            cout << "Matching index found at:" << i - j << endl;
            j = mpNext[j];  //匹配后面的子串
            flag = true;
        }
    }
    if (!flag)
    {
        cout << "Unsuccessful match=-====!";
    }
}

int main(int argc, char** argv)
{
    string p1 = "abcabcad";
    string p2 = "adcadcad";
    string p3 = "ababcaabc";
    string t = "ctcabcabcadtcaabcabcaaatabcabcad";

    cout << "MP_p1 : " << endl;
    MP(p1, t);
    cout << endl;

    cout << "MP_p2 : " << endl;
    MP(p2, t);
    cout << endl;

    cout << "MP_p3 : " << endl;
    MP(p3, t);
    cout << endl;

    string t1 = "ctcaatcacaatcat";
    string p4 = "caatcat";
    MP(p4, t1);
    cout << endl;
    return 0;
}