【HDOJ】4513 吉哥系列故事——完美队形II

  1 /* 4513 */
  2 #include <iostream>
  3 #include <string>
  4 #include <map>
  5 #include <queue>
  6 #include <set>
  7 #include <stack>
  8 #include <vector>
  9 #include <deque>
 10 #include <algorithm>
 11 #include <cstdio>
 12 #include <cmath>
 13 #include <ctime>
 14 #include <cstring>
 15 #include <climits>
 16 #include <cctype>
 17 #include <cassert>
 18 #include <functional>
 19 #include <iterator>
 20 #include <iomanip>
 21 using namespace std;
 22 //#pragma comment(linker,"/STACK:102400000,1024000")
 23 
 24 #define sti                set<int>
 25 #define stpii            set<pair<int, int> >
 26 #define mpii            map<int,int>
 27 #define vi                vector<int>
 28 #define pii                pair<int,int>
 29 #define vpii            vector<pair<int,int> >
 30 #define rep(i, a, n)     for (int i=a;i<n;++i)
 31 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 32 #define clr                clear
 33 #define pb                 push_back
 34 #define mp                 make_pair
 35 #define fir                first
 36 #define sec                second
 37 #define all(x)             (x).begin(),(x).end()
 38 #define SZ(x)             ((int)(x).size())
 39 #define lson            l, mid, rt<<1
 40 #define rson            mid+1, r, rt<<1|1
 41 
 42 const int maxn = 1e5+5;
 43 int a[maxn], b[maxn*2];
 44 int Len[maxn*2];
 45 
 46 void init(int n) {
 47     int j = 0;
 48     
 49     b[j++] = -1;
 50     b[j++] = 0;
 51     rep(i, 0, n) {
 52         b[j++] = a[i];
 53         b[j++] = 0;
 54     }
 55 }
 56 
 57 void manacher(int m) {
 58     int n = 2*m+1;
 59     int p = 0, p0 = 0;
 60     int lid, rid;
 61     
 62     rep(i, 1, n+1) {
 63         if (p > i)
 64             Len[i] = min(p-i, Len[2*p0-i]);
 65         else
 66             Len[i] = 1;
 67         
 68         while (b[i+Len[i]] == b[i-Len[i]]) {
 69             if (b[i+Len[i]] > 0) {
 70                 lid = i - Len[i];
 71                 rid = i + Len[i];
 72                 if (b[lid]>b[lid+2] || b[rid]>b[rid-2])
 73                     break;
 74             }
 75             ++Len[i];
 76         }
 77         
 78         if (i+Len[i] > p) {
 79             p = i + Len[i];
 80             p0 = i;
 81         }
 82     }
 83 }
 84 
 85 void solve(int n) {
 86     init(n);
 87     manacher(n);
 88     
 89     int ans = 0;
 90     
 91     n = n*2+1;
 92     rep(i, 1, n) {
 93         ans = max(ans, Len[i]);
 94     }
 95     printf("%d\n", ans-1);
 96 }
 97 
 98 int main() {
 99     ios::sync_with_stdio(false);
100     #ifndef ONLINE_JUDGE
101         freopen("data.in", "r", stdin);
102         freopen("data.out", "w", stdout);
103     #endif
104     
105     int t;
106     int n;
107     
108     scanf("%d", &t);
109     while (t--) {
110         scanf("%d", &n);
111         rep(i, 0, n)
112             scanf("%d", &a[i]);
113         solve(n);
114     }
115     
116     #ifndef ONLINE_JUDGE
117         printf("time = %d.\n", (int)clock());
118     #endif
119     
120     return 0;
121 }