UVa1608 UVaLive6258 Non-boring sequences

填坑系列(p.248)

比较神

从两端枚举

最坏复杂度就成O(nlogn)了

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<cstring>
#include<string>

using namespace std;

void setIO(const string& a) {
    freopen((a + ".in").c_str(), "r", stdin);
    freopen((a + ".out").c_str(), "w", stdout);
}

template<typename Q> void read(Q& x) {
    static char c;
    static bool f;
    for(f = 0; c = getchar(), !isdigit(c); ) if(c == '-') f = 1;
    for(x = 0; isdigit(c); c = getchar()) x = x * 10 + c - '0';
    if(f) x = -x;
}
template<typename Q> Q read() {
    static Q x; read(x);
    return x;
}

const int N = 200000 + 10;

int a[N], lp[N], rp[N];

#include<map>
map<int, int> cur;

bool unique(int p, int l, int r) {
    return lp[p] < l && rp[p] > r;
}

bool check(int L, int R) {
    if(L >= R) return 1;
    for(int k = 0; L + k <= R - k; k++) {
        if(unique(L + k, L, R)) return check(L, L + k - 1) && check(L + k + 1, R);
        if(unique(R - k, L, R)) return check(L, R - k - 1) && check(R - k + 1, R);
    }
    return 0;
}

int main() {
#ifdef DEBUG
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif
    
    int T = read<int>();
    while(T--) {
        int n = read<int>();
        cur.clear();
        for(int i = 1; i <= n; i++) {
            read(a[i]);
            if(cur.count(a[i])) lp[i] = cur[a[i]];
            else lp[i] = 0;
            cur[a[i]] = i;
        }
        cur.clear();
        for(int i = n; i >= 1; i--) {
            if(cur.count(a[i])) rp[i] = cur[a[i]];
            else rp[i] = n + 1;
            cur[a[i]] = i;
        }
        puts(check(1, n) ? "non-boring" : "boring");
    }
    
    return 0;
}