Minimal Labels CodeForces - 825E Topological Sort Greedy [Template]

Original title link:
E. Minimal Labels

The main idea of ​​the title:
give an undirected graph
reverse topological sorting

Analysis:
The general steps of topological sorting labeling are from small to large, and there will be situations from large to small,
so as long as the edges are built in reverse, the numbering can be reversed.

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int,int> pii;
#define mem(s,t) memset(s,t,sizeof(s))
#define D(v) cout<<#v<<" "<<v<<endl
#define inf 0x3f3f3f3f
#define pb push_back

//#define LOCAL
const int mod=1e9+7;
const int MAXN =1e5+10;
vector<int> a[MAXN];
int vis[MAXN];
priority_queue<int,vector<int> > q;
int ans[MAXN];
int main() {
#ifdef LOCAL
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
#endif
    int n,m,N;
    cin>>n>>m;
    N=n;
    for(int i=1;i<=m;i++){
        int x,y;
        cin>>x>>y;
        a[y].pb(x);
        vis[x]++;
    }
    for(int i=1;i<=n;i++){
        if(!vis[i]) q.push(i);
    }
    while(!q.empty()){
        int t=q.top();
        q.pop();
        ans[t]=N--;
        for(int i=0;i<a[t].size();i++){
            vis[a[t][i]]--;
            if(!vis[a[t][i]]) q.push(a[t][i]);
        }
    }
    for(int i=1;i<=n;i++) cout<<ans[i]<<" ";
    cout<<endl;
    return 0;
}

PS.
Forward topological sorting (template):

//拓扑排序 ① 
#include <cstdio>  
#include <cstring>  
#define MAXN 517  
int G[MAXN][MAXN];//路径  
int in_degree[MAXN];//入度  
int ans[MAXN];  
int n, m, x, y;  
int i, j;  

void toposort()  
{  
    for(i = 1; i <= n; i++)  
    {  
        for(j = 1; j <= n; j++)  
        {  
            if(G[i][j])  
            {  
                in_degree[j]++;  
            }  
        }  
    }  
    for(i = 1; i <= n; i++)//从最小的开始寻找，  
    {//这样保证了有多个答案时序号小的先输出  
        int k = 1;  
        while(in_degree[k] != 0)//寻找入度为零的点  
            k++;  
        ans[i] = k;  
        in_degree[k] = -1;  
        //更新为-1，后边检测不受影响，相当于删除节点  
        for(int j = 1; j <= n; j++)  
        {  
            if(G[k][j])  
                in_degree[j]--;//相关联的入度减1  
        }  
    }  
}  

void init()  
{  
    memset(in_degree,0,sizeof(in_degree));  
    memset(ans,0,sizeof(ans));  
    memset(G,0,sizeof(G));  
}  

int main()  
{  
    while(~scanf("%d%d",&n,&m))  
    {  
        init();  
        for(i = 0; i < m; i++)  
        {  
            scanf("%d%d",&x,&y);  
            G[x][y] = 1;  
        }  
        toposort();  
        for(i = 1; i < n; i++)  
            printf("%d ",ans[i]);  
        printf("%d\n",ans[n]);  
    }  
    return 0;  
}  

//优先队列+拓扑排序
#include<iostream>  
#include<queue>  
#include<cstdio>  
#include<cstring>  
using namespace std;  
bool map[517][517];  
int in[517];  
priority_queue<int,vector<int>,greater<int> > q;  
void topo(int n)  
{  
    for(int i=1;i<=n;i++)  
    {  
        if(in[i]==0)  
            q.push(i);  
    }  
    int c=1;  
    while(!q.empty())  
    {  
        int v=q.top();  
        q.pop();  
        if(c!=n)  
        {  
            cout<<v<<" ";  
            c++;  
        }  
        else  
            cout<<v<<endl;  
        for(int i=1;i<=n;i++)  
        {  
            if(!map[v][i])  
                continue;  
            in[i]--;  
            if(!in[i])  
                q.push(i);  

        }  
    }  
}  
int main()  
{  
    int n,m,i,j;  
    while(cin>>n>>m)  
    {  
        int k=0;  
        memset(map,0,sizeof map);  
        memset(in,0,sizeof in);  
        while(m--)  
        {  
            cin>>i>>j;  
            if(map[i][j])  
                continue;  
            map[i][j]=1;  
            in[j]++;  
        }  
        topo(n);  
    }  
}