manacher 算法 O（n）最长回文子串

 1 #include <map>
 2 #include <set>
 3 #include <list>
 4 #include <stack>
 5 #include <queue>
 6 #include <cmath>
 7 #include <ctime>
 8 #include <cstdio>
 9 #include <vector>
10 #include <cstdlib>
11 #include <complex>
12 #include <cstring>
13 #include <iostream>
14 #include <algorithm>
15 
16 #define REP(i,N) for (int i = 0;i < (N);i++)
17 #define REP_1(i,N) for (int i = 1;i < (N);i++)
18 #define REP_2(i,be,en) for (int i = (be);i < (en);i++)
19 #define DWN(i,N) for (int i = (N);i >= 0;i--)
20 #define DWN_1(i,N) for (int i = (N);i >= 1;i--)
21 #define DWN_2(i,en,be) for (int i = (en);i >= (be);i--)
22 #define INF 0x3f3f3f3f
23 #define MAXN 1000100
24 #define FR(N) freopen((N),"r",stdin)
25 #define FW(N) freopen((N),"w",stdout)
26 #define GETS(ch) fgets((ch),MAXN,stdin);
27 using namespace std;
28 
29 typedef long long LL;
30 typedef map<string,int> MINT;
31 typedef vector<int> VINT;
32 
33 const int M = 110010*2;
34 char str[M];//start from index 1
35 int p[M];
36 char s[M];
37 int n;
38 void checkmax(int &ans,int b){
39     if(b>ans) ans=b;
40 }
41 inline int min(int a,int b){
42     return a<b?a:b;
43 }
44 void kp(){
45     int i;
46     int mx = 0;
47     int id;
48     REP_1(i,n) {
49         if( mx > i )
50             p[i] = min( p[2*id-i], p[id]+id-i );
51         else
52             p[i] = 1;
53         for(; str[i+p[i]] == str[i-p[i]]; p[i]++) ;
54         if( p[i] + i > mx ) {
55             mx = p[i] + i;
56             id = i;
57         }
58     }
59 }
60 void pre() {
61     int i,j,k;
62     n = strlen(s);
63     str[0] = ‘$‘;
64     str[1] = ‘#‘;
65     REP(i,n) {
66         str[i*2 + 2] = s[i];
67         str[i*2 + 3] = ‘#‘;
68     }
69     n = n*2 + 2;
70     str[n] = 0;
71 }
72 
73 void pt() {
74     int i;
75     int ans = 0;
76     REP(i,n)
77         checkmax(ans, p[i]);
78     printf("%d\n", ans-1);
79 }
80 
81 int main() {
82     //FR("1.txt");
83     int _=0;
84     int N;
85     cin >> N;
86     while( N-- ) {
87         scanf("%s", s);
88         pre();
89         kp();
90         pt();
91     }
92     return 0;
93 }