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文章目錄

• 題意：
• 思路：

題意：

求$s$中本質不同的字串個數。

$1\le |s|\le 1e5$

思路：

顯然， 個數就是$\sum (len[i]?len[fa[i]])$。

//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math") //#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native") //#pragma GCC optimize(2) #include<cstdio> #include<iostream> #include<string> #include<cstring> #include<map> #include<cmath> #include<cctype> #include<vector> #include<set> #include<queue> #include<algorithm> #include<sstream> #include<ctime> #include<cstdlib> #include<random> #include<cassert> #define X first #define Y second #define L (u<<1) #define R (u<<1|1) #define pb push_back #define mk make_pair #define Mid ((tr[u].l+tr[u].r)>>1) #define Len(u) (tr[u].r-tr[u].l+1) #define random(a,b) ((a)+rand()%((b)-(a)+1)) #define db puts("---") using namespace std;//void rd_cre() { freopen("d://dp//data.txt","w",stdout); srand(time(NULL)); } //void rd_ac() { freopen("d://dp//data.txt","r",stdin); freopen("d://dp//AC.txt","w",stdout); } //void rd_wa() { freopen("d://dp//data.txt","r",stdin); freopen("d://dp//WA.txt","w",stdout); }typedef long long LL; typedef unsigned long long ULL; typedef pair<int,int> PII;const int N=2000010,mod=1e9+7,INF=0x3f3f3f3f; const double eps=1e-6;int last=1,tot=1,len; int cnt[N]; char s[N]; struct Node {int ch[26];int len,fa; }sam[N*2]; vector<int>v[N];void add(int c) {int p=last,np=last=++tot; cnt[tot]=1;sam[np].len=sam[p].len+1;while(p&&!sam[p].ch[c]) {sam[p].ch[c]=np;p=sam[p].fa;} if(!p) sam[np].fa=1;else {int q=sam[p].ch[c];if(sam[q].len==sam[p].len+1) sam[np].fa=q;else {int nq=++tot; sam[nq]=sam[q];sam[nq].len=sam[p].len+1;sam[q].fa=sam[np].fa=nq;while(p&&sam[p].ch[c]==q) {sam[p].ch[c]=nq;p=sam[p].fa;}}} }LL ans=0;int main() { // ios::sync_with_stdio(false); // cin.tie(0);int n;scanf("%d%s",&n,s+1);int len=strlen(s+1);for(int i=1;i<=len;i++) add(s[i]-'a');for(int i=2;i<=tot;i++) ans+=sam[i].len-sam[sam[i].fa].len;cout<<ans<<endl;return 0; } /**/```cpp // Problem: P2408 不同子串個數 // Contest: Luogu // URL: https://www.luogu.com.cn/problem/P2408 // Memory Limit: 125 MB // Time Limit: 1000 ms // // Powered by CP Editor (https://cpeditor.org)//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math") //#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native") //#pragma GCC optimize(2) #include<cstdio> #include<iostream> #include<string> #include<cstring> #include<map> #include<cmath> #include<cctype> #include<vector> #include<set> #include<queue> #include<algorithm> #include<sstream> #include<ctime> #include<cstdlib> #include<random> #include<cassert> #define X first #define Y second #define L (u<<1) #define R (u<<1|1) #define pb push_back #define mk make_pair #define Mid ((tr[u].l+tr[u].r)>>1) #define Len(u) (tr[u].r-tr[u].l+1) #define random(a,b) ((a)+rand()%((b)-(a)+1)) #define db puts("---") using namespace std;//void rd_cre() { freopen("d://dp//data.txt","w",stdout); srand(time(NULL)); } //void rd_ac() { freopen("d://dp//data.txt","r",stdin); freopen("d://dp//AC.txt","w",stdout); } //void rd_wa() { freopen("d://dp//data.txt","r",stdin); freopen("d://dp//WA.txt","w",stdout); }typedef long long LL; typedef unsigned long long ULL; typedef pair<int,int> PII;const int N=1000010,mod=1e9+7,INF=0x3f3f3f3f; const double eps=1e-6;int last=1,tot=1,len; int cnt[N],n; char s[N]; LL ans[N]; struct Node {int ch[26];int len,fa; }sam[N*2];void add(int c) {int p=last,np=last=++tot; sam[np].len=sam[p].len+1;while(p&&!sam[p].ch[c]) {sam[p].ch[c]=np;p=sam[p].fa;}if(!p) sam[np].fa=1;else {int q=sam[p].ch[c];if(sam[p].len+1==sam[q].len) sam[np].fa=q;else {int nq=++tot;sam[nq]=sam[q];sam[nq].len=sam[p].len+1;sam[q].fa=sam[np].fa=nq;while(p&&sam[p].ch[c]==q) {sam[p].ch[c]=nq;p=sam[p].fa;}}} }LL dfs(int u) {if(ans[u]) return ans[u];for(int i=0;i<26;i++) if(sam[u].ch[i]) dfs(sam[u].ch[i]),ans[u]+=ans[sam[u].ch[i]]+1;return ans[u]; }int main() { // ios::sync_with_stdio(false); // cin.tie(0);scanf("%d%s",&n,s+1);for(int i=1;i<=n;i++) add(s[i]-'a');printf("%lld\n",dfs(1));return 0; } /**/

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