BZOJ1511: [POI2006]OKR-Periods of Words

 1 #include<cstdio>
 2 
 3 #include<cstdlib>
 4 
 5 #include<cmath>
 6 
 7 #include<cstring>
 8 
 9 #include<algorithm>
10 
11 #include<iostream>
12 
13 #include<vector>
14 
15 #include<map>
16 
17 #include<set>
18 
19 #include<queue>
20 
21 #include<string>
22 
23 #define inf 1000000000
24 
25 #define maxn 1000000+5
26 
27 #define maxm 500+100
28 
29 #define eps 1e-10
30 
31 #define ll long long
32 
33 #define pa pair<int,int>
34 
35 #define for0(i,n) for(int i=0;i<=(n);i++)
36 
37 #define for1(i,n) for(int i=1;i<=(n);i++)
38 
39 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
40 
41 #define for3(i,x,y) for(int i=(x);i>=(y);i--)
42 
43 #define mod 1000000007
44 
45 using namespace std;
46 
47 inline int read()
48 
49 {
50 
51     int x=0,f=1;char ch=getchar();
52 
53     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
54 
55     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
56 
57     return x*f;
58 
59 }
60 int n,next[maxn];
61 ll ans;
62 char s[maxn];
63 
64 int main()
65 
66 {
67 
68     freopen("input.txt","r",stdin);
69 
70     freopen("output.txt","w",stdout);
71 
72     n=read();
73     scanf("%s",s+1);
74     for(int i=2,j=0;i<=n;i++)
75     {
76         while(j&&s[j+1]!=s[i])j=next[j];
77         if(s[j+1]==s[i])j++;
78         next[i]=j;
79     }
80     for1(i,n)if(next[next[i]]!=0)next[i]=next[next[i]];
81     for1(i,n)if(next[i])ans+=(ll)(i-next[i]);
82     printf("%lld\n",ans);
83 
84     return 0;
85 
86 }