HDU

HDU - 5406

排序之后就变成了求两个不相交的最长LIS， 用树状数组把n ^ 3 的dp 优化成 n ^ 2 * log(n) 就ok 了。

#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define ull unsigned long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ALL(x) (x).begin(), (x).end()
#define fio ios::sync_with_stdio(false); cin.tie(0);

using namespace std;

const int N = 1000 + 2;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const double PI = acos(-1);

template<class T, class S> inline void add(T &a, S b) {a += b; if(a >= mod) a -= mod;}
template<class T, class S> inline void sub(T &a, S b) {a -= b; if(a < 0) a += mod;}
template<class T, class S> inline bool chkmax(T &a, S b) {return a < b ? a = b, true : false;}
template<class T, class S> inline bool chkmin(T &a, S b) {return a > b ? a = b, true : false;}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int n, tot, dp[N][N], hs[N];

struct Bit {
    int a[N];
    void init() {
        for(int i = 1; i <= tot; i++) {
            a[i] = 0;
        }
    }
    void modify(int x, int v) {
        for(int i = x; i <= tot; i += i & -i) {
            chkmax(a[i], v);
        }
    }
    int preMax(int x) {
        int ans = 0;
        for(int i = x; i; i -= i & -i) {
            chkmax(ans, a[i]);
        }
        return ans;
    }
} big[N], sml[N];

PII apple[N];
int a[N];

int main() {

    int T; scanf("%d", &T);
    while(T--) {
        scanf("%d", &n);
        tot = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%d%d", &apple[i].fi, &apple[i].se);
            hs[++tot] = apple[i].se;
        }
        hs[++tot] = 0;

        if(n == 1) {
            puts("1");
            continue;
        }
        sort(apple + 1, apple + 1 + n, [&](PII a, PII b) {
            if(a.fi == b.fi) return a.se < b.se;
            else return a.fi > b.fi;
        });
        sort(hs + 1, hs + 1 + tot);
        tot = unique(hs + 1, hs + 1 + tot) - hs - 1;

        for(int i = 0; i <= n; i++) {
            a[i] = lower_bound(hs + 1, hs + 1 + tot, apple[i].se) - hs;
        }

        for(int i = 0; i <= n; i++) {
            big[i].init();
            sml[i].init();
        }

        int ans = 0;
        for(int i = 1; i <= n; i++) {
            for(int j = 0; j < i; j++) {
                dp[i][j] = j ? 2 : 1;
                chkmax(dp[i][j], sml[j].preMax(a[i]) + 1);
                chkmax(dp[i][j], big[j].preMax(a[i]) + 1);
                big[i].modify(a[j], dp[i][j]);
                sml[j].modify(a[i], dp[i][j]);
                chkmax(ans, dp[i][j]);
            }
        }
        printf("%d
", ans);
    }
    return 0;
}

/*
*/