编程测评

问题如下

代码如下

#include <bits/stdc++.h>using namespace std;//KMP算法 int KMP(const string& target,const string& pattern){    const int target_length = target.size();    const int pattern_length = pattern.size();    int * overlay_value = new int[pattern_length];    overlay_value[0] = -1;    int index = 0;    for(int i=1;i<pattern_length;++i)    {        index = overlay_value[i-1];        while(index>=0 && pattern[index+1]!=pattern[i])        {            index  = overlay_value[index];        }        if(pattern[index+1]==pattern[i])        {            overlay_value[i] = index +1;        }        else        {            overlay_value[i] = -1;        }    }    //match algorithm start    int pattern_index = 0;    int target_index = 0;    while(pattern_index<pattern_length&&target_index<target_length)    {        if(target[target_index]==pattern[pattern_index])        {            ++target_index;            ++pattern_index;        }        else if(pattern_index==0)        {            ++target_index;        }        else        {            pattern_index = overlay_value[pattern_index-1]+1;        }    }    if(pattern_index==pattern_length)    {        return target_index-pattern_index;    }    else    {        return -1;    }    delete [] overlay_value;}int main(){    int n;    string s;    vector<string> vec;    while(cin>>n){        for(int i = 0;i<2*n;++i){            cin>>s;            vec.push_back(s);        }        string a[1000];        vector<string>::iterator it=vec.begin();        for(int i = 0;i<2*n&&it!=vec.end();++i,++it){                            a[i]=*it;        }         for(int i =0;i<2*n;i+=2){             cout<<KMP(a[i],a[i+1])<<endl;        }    }    return 0;}

代码只是找出了第一个与字符相匹配的字符串位置，还是有缺陷的，需要改进。