CF4D Mysterious Present 二维偏序+dp

题目

求一个二维的严格递增序列。我们先排个序，然后再dp严格递增子序列，记录一下是从哪里转移过来的。然后再递归输出路径即可。

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int INF = 0x3f3f3f3f;
const double Pi = acos(-1);
namespace {
	template <typename T> inline void read(T &x) {
		x = 0;
		T f = 1;
		char s = getchar();
		for(; !isdigit(s); s = getchar()) if(s == '-') f = -1;
		for(;  isdigit(s); s = getchar()) x = (x << 3) + (x << 1) + (s ^ 48);
		x *= f;
	}
}
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define _for(n,m,i) for (register int i = (n); i <  (m); ++i)
#define _rep(n,m,i) for (register int i = (n); i <= (m); ++i)
#define _srep(n,m,i)for (register int i = (n); i >= (m); i--)
#define _sfor(n,m,i)for (register int i = (n); i >  (m); i--)
#define lson rt << 1, l, mid
#define rson rt << 1 | 1, mid + 1, r
#define lowbit(x) x & (-x)
#define pii pair<int,int>
#define fi first
#define se second
const int N = 5e3+5;
struct node {
	int w, h, id;
	bool operator < (const node &x) const {
		return w == x.w ? h < x.h : w < x.w;
	}
} e[N];
int dp[N], pos[N];
void print(int x) {
	if(!x) return ;
	print(pos[x]);
	printf("%d ", e[x].id);
}
int main() {
	int n, w, h, cnt = 0;
	read(n);read(w);read(h);
	for(int i = 1; i <= n; i++) {
		read(e[0].w);read(e[0].h);e[0].id = i;
		if(e[0].w > w  && e[0].h > h) e[++cnt] = e[0];
	}
	if(!cnt) return 0*puts("0");
	int ans = 0, st = 0;
	e[0].h = e[0].id = e[0].w = 0;
	sort(e + 1, e + cnt + 1);
	for(int i = 1; i <= cnt; i++)
		for(int j = 0; j < i; j++)
			if(e[i].w > e[j].w && e[i].h > e[j].h) {
				if(dp[i] < dp[j] + 1)
					dp[i] = dp[j]+1, pos[i] = j;
				if(dp[i] > ans)
					ans = dp[i], st = i;
			}
	printf("%d\n", ans);
	print(st);
}