HDU I'm Telling the Truth (二分图最大匹配+字典序最大路径输出（好题）)

关键在于建图，把 每个学生和它的可能的名次之间连上边，然后最大匹配，匹配时逆序进行（保证字典序的最大）

#include<cstdio>#include<iostream>#include<algorithm>#include<cmath>#include<set>#include<map>#include<string>#include<cstring>#include<stack>#include<queue>#include<vector>#include<cstdlib>#define lson (rt<<1),L,M#define rson (rt<<1|1),M+1,R#define M ((L+R)>>1)#define cl(a,b) memset(a,b,sizeof(a));#define LL long long#define P pair<int,int>#define X first#define Y second#define pb push_back#define fread(zcc)  freopen(zcc,"r",stdin)#define fwrite(zcc) freopen(zcc,"w",stdout)using namespace std;const int maxn=100005;const int inf=999999;vector<int> G[maxn];int matching[maxn];bool vis[maxn];int num_left;bool as[maxn];int dfs(int u){    int N=G[u].size();    for(int i=0;i<N;i++){        int v=G[u][i];        if(vis[v])continue;        vis[v]=true;        if(matching[v]==-1||dfs(matching[v])){            matching[v]=u;            as[u]=true;            return 1;        }    }    return 0;}int hungar(){    int ans=0;    cl(matching,-1);    cl(as,false);    for(int i=num_left-1;i>=0;i--){        cl(vis,false);        ans+=dfs(i);    }    return ans;}int main(){    int T;    scanf("%d",&T);    while(T--){        int n,x,y;        scanf("%d",&n);        for(int i=0;i<n;i++){            scanf("%d%d",&x,&y);            for(int j=x;j<=y;j++){                G[i].pb(j);            }        }        num_left=n;        int sum=hungar();//匹配的时候逆序        printf("%d\n",sum);        for(int i=0;i<n-1;i++){            if(as[i]){                printf("%d ",i+1);            }        }        printf("%d\n",n);        for(int i=0;i<maxn;i++)G[i].clear();    }    return 0;}