图的遍历

 1 #include <queue>
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 const int maxn = 100000 + 10;
 7 queue<int> Q;
 8 int n, m, S, T, ms = 0, fch[maxn], ans = 0;
 9 bool vis[maxn];
10 struct Tedge{
11     int to, next;
12 }adj[maxn];
13 void read(int &x){
14     x = 0; int sig = 1; char ch = getchar();
15     while(!isdigit(ch)) { if(ch == ‘-‘) sig = -1; ch = getchar(); }
16     while(isdigit(ch)) { x = 10 * x + ch - ‘0‘; ch = getchar(); }
17     x *= sig; return ;
18 }
19 void AddEdge(int u, int v){
20     adj[ms].next = fch[u];
21     adj[ms].to = v;
22     fch[u] = ms ++;
23     return ;
24 }
25 void BFS(){
26     Q.push(S); vis[S] = true; ans ++;
27     while(!Q.empty()){
28         int x = Q.front(); Q.pop();
29         for(int i = fch[x]; i != -1; i = adj[i].next){
30             int v = adj[i].to;
31             if(!vis[v]){
32                 vis[v] = true;
33                 Q.push(v);
34                 ans ++;
35             }
36         }
37     }
38     return ;
39 }
40 void init(){
41     memset(fch, -1, sizeof(fch));
42     int u, v;
43     read(n); read(m);
44     for(int i = 0; i < m; i ++){
45         read(u); read(v);
46         AddEdge(u, v);
47     }
48     S = 1; T = n;
49     return ;
50 }
51 void print(){
52     printf("%d\n", ans);
53     return ;
54 }
55 int main(){
56     init();
57     BFS();
58     print();
59     return 0;
60 }

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int maxn = 100000 + 10;
int n, m, S, T, ms = 0, fch[maxn], ans = 0;
bool vis[maxn];
struct Tedge{
    int to, next;
}adj[maxn];
void read(int &x){
    x = 0; int sig = 1; char ch = getchar();
    while(!isdigit(ch)) { if(ch == ‘-‘) sig = -1; ch = getchar(); }
    while(isdigit(ch)) { x = 10 * x + ch - ‘0‘; ch = getchar(); }
    x *= sig; return ;
}
void AddEdge(int u, int v){
    adj[ms].next = fch[u];
    adj[ms].to = v;
    fch[u] = ms ++;
    return ;
}
void DFS(int x){
    if(vis[x]) return ;
    ans ++;    vis[x] = true;
    for(int i = fch[x]; i != -1; i = adj[i].next)
        DFS(adj[i].to);
    return ;
}
void init(){
    memset(fch, -1, sizeof(fch));
    int u, v;
    read(n); read(m);
    for(int i = 0; i < m; i ++){
        read(u); read(v);
        AddEdge(u, v);
    }
    S = 1; T = n;
    return ;
}
void print(){
    printf("%d\n", ans);
    return ;
}
int main(){
    init();
    DFS(S);
    print();
    return 0;
}