hihocoder 1015题

代码

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

int KMP(const string &pattern,const string &str)
{
    const int len1 = pattern.length();
    const int len2 = str.length();
    vector<int> next(len1);
    next[0]=0;
    int i,j,k;
    for (i=1;i<len1;i++)
    {
        k=next[i-1];
        while (pattern[i] != pattern[k]&&k!=0)
        {
            k=next[k-1];
        }
        if(pattern[i] == pattern[k])
            next[i]=k+1;
        else
            next[i]=0;
    }
    i=j=0;
    int mycount=0;
    while (j < len2)
    {
        if (pattern[i]!=str[j])
        {
            if (i==0)
            {
                i=0;
                j++;
            }
            else
                i=next[i-1];
        }
        else
        {
            i++;
            j++;
            if(pattern[i] == '')
            {
                mycount++;
                i=next[len1-1];//为什么取pattern最后一个字符的next，自己想
                //i赋值位next[len1-1]是为了防止j回溯
            }
        }
    }

    return mycount;
}

int main()
{
    int n;
    string pattern,str;
    while (cin >> n)
    {
        while (n--)
        {
            cin >> pattern >> str;
            cout << KMP(pattern,str)<<endl;
        }
    }
    return 0;
}