字符串模式匹配

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/***********************************输入：主串sa, 子串sb, 开始匹配位置start*输出：成功返回sb首字符在sa的位置，否则返回-1***********************************/#include <iostream>#include <string>#include <vector>using namespace std;/********朴素模式匹配********************/int StringMatch(string &sa, string &sb, unsigned start){    if (sa.size() == 0 || sb.size() == 0)        return -1;    if (sa.size() < sb.size())        return -1;    unsigned starta = start, startb = 0;    while (starta < sa.size() - sb.size() + 1)    {        unsigned i = starta;        unsigned j = startb;        while (j < sb.size())        {                       if (sa[i] != sb[j])                break;            ++i;            ++j;        }        if (j == sb.size())            return starta;        ++starta;    }    return -1;}/******KMP模式匹配********************//*next*/void GetNext(string &m, vector<int> &next){    int i = -1, j = 0;    next[0] = 0;    while (j < int(m.size()))    {        if (i == -1||m[i] == m[j])        {            i++;            j++;                        next[j] = i + 1;        }        else            i = next[i] - 1;    }    return;}/*nextval*/void GetNextval(string &m, vector<int> &next){    int i = -1, j = 0;    next[0] = 0;    while (j < int(m.size()))    {        if (i == -1 || m[i] == m[j])        {            i++;            j++;            if (m[i] != m[j])                next[j] = i + 1;            else                next[j] = next[i];        }        else            i = next[i] - 1;    }    return;}/*KMP*/int KMPStringMatch(string &sa, string &sb, unsigned start){    if (sa.size() == 0 || sb.size() == 0)        return -1;    if (sa.size() < sb.size())        return -1;    vector<int> next(sa.size() + 1);    GetNext(sa, next);    unsigned starta = start, startb = 0;    while (starta < sa.size() - sb.size() + 1)    {        unsigned i = starta;        unsigned j = startb;        while (j < sb.size())        {            if (sa[i] != sb[j])            {                startb = next[j];                break;            }            ++i;            ++j;        }        if (j == sb.size())            return starta;        ++starta;    }    return -1;}int main(){    string a = "0000000000000000000000000000000000000001";    string b = "00000000001";    cout << KMPStringMatch(a, b, 0) << endl;    return 0;}
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