poj 2774

来源：互联网发布：阿里云学生认证被锁编辑：程序博客网时间：2024/04/29 10:45

最长公共子串

#include <iostream>#include <stdio.h>#include <algorithm>#include <string>#define maxn 100010 * 2using namespace std;int n, k;int rank[maxn];int tmp[maxn];int sa[maxn], lcp[maxn];string S,T;bool compara_sa(int i, int j){if(rank[i] != rank[j]) return rank[i] < rank[j];else{int ri = i + k <= n ? rank[i + k] : -1;int rj = j + k <= n ? rank[j + k] : -1;return ri < rj;}}void construct_sa(string S, int *sa){n = S.length();for(int i = 0;i <= n;i++){sa[i] = i;rank[i] = i < n ? S[i] : -1;}for(k = 1;k <= n;k *= 2){sort(sa, sa + n + 1, compara_sa);tmp[sa[0]] = 0;for(int i = 1;i <= n;i++){tmp[sa[i]] = tmp[sa[i - 1]] + (compara_sa(sa[i - 1], sa[i]) ? 1 : 0);}for(int i = 0;i <= n;i++){rank[i] = tmp[i];}}}void construct_lcp(string S, int *sa, int *lcp){int n = S.length();for(int i = 0;i <= n;i++) rank[sa[i]] = i;int h = 0;lcp[0] = 0;for(int i = 0;i < n;i++){int j = sa[rank[i] - 1];if(h > 0) h--;for(;j + h < n&&i + h < n;h++){if(S[j + h] != S[i + h]) break;}lcp[rank[i] - 1] = h;}}void solve(){int s1 = S.length();S += '\0' + T;construct_sa(S, sa);construct_lcp(S, sa, lcp);int ans = 0;for(int i = 0;i < S.length();i++){if((sa[i] < s1) != (sa[i + 1] < s1)){ans = max(ans, lcp[i]);}}printf("%d\n", ans);}int main(){while(cin>>S>>T)solve();}

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