National Property CodeForces - 875C (拓扑排序)

大意: n个字符串, 每次操作选出一种字符全修改为大写, 求判断能否使n个字符串字典序非降.

建源点s, 汇点t, s与所有必须转大写的连边, 必须不转大写的与t连边.

#include <iostream>
#include <algorithm>
#include <math.h>
#include <cstdio>
#include <set>
#include <map>
#include <string>
#include <vector>
#include <string.h>
#include <queue>
#define PER(i,a,n) for(int i=n;i>=a;--i)
#define REP(i,a,n) for(int i=a;i<=n;++i)
#define hr putchar('\n')
#define pb push_back
#define mp make_pair
#define mid (l+r>>1)
#define lc (o<<1)
#define rc (lc|1)
#define FI first
#define SE second

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int P = 1e9+7;
ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}
ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}
ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}
//head

const int N = 4e5+10;
int a[N], b[N], c[N], vis[N], f[N], n, m, k, t;
vector<int> s[N], g[N];

void dfs(int x) {
	if (vis[x]) return;
	vis[x] = 1;
	for (int y:g[x]) dfs(y);
}

int main() {
	scanf("%d%d", &n, &m);
	REP(i,1,n) {
		scanf("%d", &t);
		while (t--) scanf("%d",&k),s[i].pb(k);
	}
	REP(i,1,n-1) {
		int pos = 0;
		for (; pos<s[i].size()&&pos<s[i+1].size()&&s[i][pos]==s[i+1][pos]; ++pos);
		if (pos==s[i].size()) continue;
		if (pos==s[i+1].size()) return puts("No"),0;
		if (s[i][pos]>s[i+1][pos]) {
			g[0].pb(s[i][pos]), g[s[i+1][pos]].pb(m+1);
		} else {
			g[s[i+1][pos]].pb(s[i][pos]);
		}
	}
	dfs(0);
	if (vis[m+1]) return puts("No"),0;
	puts("Yes");
	int ans = 0;
	REP(i,1,m) ans+=vis[i];
	printf("%d\n", ans);
	REP(i,1,m) if (vis[i]) printf("%d ", i);hr;
}