【HDOJ】4513 吉哥系列故事——完美队形II

/* 4513 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <cctype>
#include <cassert>
#include <functional>
#include <iterator>
#include <iomanip>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,1024000")

#define sti                set<int>
#define stpii            set<pair<int, int> >
#define mpii            map<int,int>
#define vi                vector<int>
#define pii                pair<int,int>
#define vpii            vector<pair<int,int> >
#define rep(i, a, n)     for (int i=a;i<n;++i)
#define per(i, a, n)     for (int i=n-1;i>=a;--i)
#define clr                clear
#define pb                 push_back
#define mp                 make_pair
#define fir                first
#define sec                second
#define all(x)             (x).begin(),(x).end()
#define SZ(x)             ((int)(x).size())
#define lson            l, mid, rt<<1
#define rson            mid+1, r, rt<<1|1

const int maxn = 1e5+5;
int a[maxn], b[maxn*2];
int Len[maxn*2];

void init(int n) {
int j = 0;

b[j++] = -1;
b[j++] = 0;
rep(i, 0, n) {
b[j++] = a[i];
b[j++] = 0;
}
}

void manacher(int m) {
int n = 2*m+1;
int p = 0, p0 = 0;
int lid, rid;

rep(i, 1, n+1) {
if (p > i)
Len[i] = min(p-i, Len[2*p0-i]);
else
Len[i] = 1;

while (b[i+Len[i]] == b[i-Len[i]]) {
if (b[i+Len[i]] > 0) {
lid = i - Len[i];
rid = i + Len[i];
if (b[lid]>b[lid+2] || b[rid]>b[rid-2])
break;
}
++Len[i];
}

if (i+Len[i] > p) {
p = i + Len[i];
p0 = i;
}
}
}

void solve(int n) {
init(n);
manacher(n);

int ans = 0;

n = n*2+1;
rep(i, 1, n) {
ans = max(ans, Len[i]);
}
printf("%d\n", ans-1);
}

int main() {
ios::sync_with_stdio(false);
#ifndef ONLINE_JUDGE
freopen("data.in", "r", stdin);
freopen("data.out", "w", stdout);
#endif

int t;
int n;

scanf("%d", &t);
while (t--) {
scanf("%d", &n);
rep(i, 0, n)
scanf("%d", &a[i]);
solve(n);
}

#ifndef ONLINE_JUDGE
printf("time = %d.\n", (int)clock());
#endif

return 0;
}