Boyer-Moore algorithm ---c++

i do not speak the algorithm principle, you can get this knowledge in my blog.

/*************************************************************************
	> File Name: Boyer_Moore.cpp
	> Author: ryq
	> Email: [email protected] 
	> Created Time: 2014年05月22日 星期四 19时30分56秒
 ************************************************************************/

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

pair<string,int> Boyer_Moore(string &src, string &des)
{
    int size = src.size();
    int len = des.size();
    string str;
    if(len > size)
        return  make_pair(str,-1);
    int i,j;
    i = j = len-1;
    int k = 0;// record the number of  good chars; 
    for(; i < size && j >= 0;){
        if(src[i] == des[j]){
            i--;
            j--;
            k++;
        }
        else{
            if(k == 0){
                size_t found = des.find_last_of(src[i]);
                if(found == string::npos)
                    i += len-1;
                else
                    i += len -1 - found;
            }
            else{
                size_t found = des.find_first_of(src[i+k]);
                if(found == len-1){
                    i = i + k + len -1;
                    j = len - 1;
                }
                else{
                    i = i + len - found - 1;
                    j = len - 1;
                } 
                k = 0;
            }
        }
    }
    if(j < 0)
        return make_pair(des,i+1);
    else
        return make_pair(str,-1);
    
}

int main()
{
    pair<string,int>res;
    string src = "BBCABCDABD ABCDABCDABE";
    string des = "BCDABE";
    res = Boyer_Moore(src,des);
    cout<<res.first<<" "<<res.second<<endl;
}


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