KMP 字符串匹配

理论参考：阮一峰老师http://www.ruanyifeng.com/blog/2013/05/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm.html

#include "stdafx.h"

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

void BuildPatchMatchTable(int *partMatchTable, char *findstr)
{
    int len = strlen(findstr); 
    if (findstr == NULL)
        return;
    partMatchTable[0] = 0;

    string findstring = string(findstr);
    string tmpstr = "";
    vector<string> prefixVec;
    vector<string> suffixVec;

    for (int i = 2; i < len+1; i++)
    {
        tmpstr = findstring.substr(0,i);
        //前缀：
        for (int j = 1; j < i; j++)
            prefixVec.push_back(tmpstr.substr(0, j));
        //后缀：
        for (int j = 1; j < i; j++)
            suffixVec.push_back(tmpstr.substr(j));

        //共有元素的最大长度
        int maxsize = 0;
        for (int j = 0; j < prefixVec.size(); j++)
        {
            int length = 0;
            auto it = find(suffixVec.begin(), suffixVec.end(), prefixVec[j]);
            if (it != suffixVec.end())
                length = prefixVec[j].size();

            maxsize = max(length, maxsize);
        }
        partMatchTable[i - 1] = maxsize;    
        prefixVec.clear();
        suffixVec.clear();
    }
}

int KMP(char *srcstr, char *findstr){
    int len = strlen(findstr);
    int *partMatchTable = new int[len];
    BuildPatchMatchTable(partMatchTable, findstr);
    
    int temp = strlen(srcstr) - strlen(findstr);
    int pos = 0;
    while (pos < temp)
    {
        int j = 0;
        for (int i = pos; i < (pos + len); i++)
        {
            if (srcstr[i] == findstr[i - pos])
            {
                ++j;
                if (j == len)
                {
                    delete partMatchTable;
                    return pos;
                }        
            }
            else
            {
                if (j == 0){
                    pos = pos + 1;
                }
                else
                {
                    pos = pos + j- partMatchTable[j - 1];
                }
                break;
            }
        }
    }
    delete partMatchTable;
    return -1; //不存在
}

int _tmain(int argc, _TCHAR* argv[])
{
    
    char srcStr[] = "bbc abcdab abcdabcdabde";
    char findStr[] = "abcdabd";
    cout << "pos:" << KMP(srcStr, findStr) << endl;
    
    system("pause");
    return 0;
}