SPOJ LCS

来源：互联网发布：网络招聘司机编辑：程序博客网时间：2024/06/02 05:43
求两个串的最长公共字串
后缀自动机模板题
#include<bits/stdc++.h>using namespace std;const int maxn = 251234,mlen = 26;int toid(char c){ return c - 'a'; }struct Node{    int len,fa,nex[mlen];    Node(int _len = 0){        len = _len;        memset(nex,fa=-1,sizeof(nex));    }    void copy(const Node & v){        for(int i=0;i<mlen;i++)             nex[i] = v.nex[i];        fa = v.fa;    }    void out(){        printf("fa = %2d len = %d ",fa,len);        for(int i=0;i<4;i++){            printf("(%c %2d)",i+'a',nex[i]);        }        puts("");    }}node[maxn*2]; int _cnt;int newNode(int len){    node[_cnt] = Node(len);    return _cnt++;}int root,omega; //在一些模板中也用last作为变量名，这里取omega作为最后一个的意思void init(){    _cnt = 0;    root = omega = newNode(0);}void extend(int x){    int ox = newNode(node[omega].len+1);    while(omega != -1 && node[omega].nex[x] == -1){        node[omega].nex[x] = ox;        omega = node[omega].fa;    }    if(omega == -1){        node[ox].fa = root;    }    else{        int omegax = node[omega].nex[x]; //omegax是omega后面添加x所转移到的状态        if(node[omega].len + 1 == node[omegax].len){            node[ox].fa = omegax;        }         else{            int megax = newNode(node[omega].len+1); //megax是omegax所分裂出来的一个后缀状态            node[megax].copy(node[omegax]);            node[ox].fa = node[omegax].fa = megax;            while(omega != -1 && node[omega].nex[x] == omegax){                node[omega].nex[x] = megax;                omega = node[omega].fa;            }        }    }    omega = ox;}void build(char *arr){    init();    for(int i=0;arr[i];i++){        extend(toid(arr[i]));    }}int run(char *arr){    int st = root;    int ret = 0,len = 0;    auto tox = [&](int s,int i){return node[s].nex[toid(arr[i])];};    for(int i=0;arr[i];i++){        if(tox(st,i) != -1){            len++;            ret = max(ret,len);            st = tox(st,i);        }        else{            while(st != -1 && tox(st,i) == -1){                st = node[st].fa;            }            if(st == -1){                len = 0;                st = 0;            }            else {                len = node[st].len+1;                st = tox(st,i);                ret = max(ret,len);            }        }    }    return ret;}char inp[maxn];int main(){    while(~scanf("%s",inp)){        build(inp);        scanf("%s",inp);        printf("%d\n",run(inp));    }    return 0;}
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