头文件

#include<cstdio>
#include<cstring>
#include<algorithm>
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define per(i,j,k) for(int i=j;i>=k;i--)
typedef long long ll;
template<typename T>void in(T &x) {
    char ch = getchar();bool flag = 0;x = 0;
    while(ch < '0' || ch > '9') flag |= (ch == '-'), ch = getchar();
    while(ch <= '9' && ch >= '0') x = (x << 1) + (x << 3) + ch - '0', ch = getchar();
    if(flag) x = -x;return ;
}

int main() {	
}

链式前向星：

#include<cstdio>
#include<cstring>
#include<algorithm>
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define per(i,j,k) for(int i=j;i>=k;i--)
typedef long long ll;
template<typename T>void in(T &x) {
    char ch = getchar();bool flag = 0;x = 0;
    while(ch < '0' || ch > '9') flag |= (ch == '-'), ch = getchar();
    while(ch <= '9' && ch >= '0') x = (x << 1) + (x << 3) + ch - '0', ch = getchar();
    if(flag) x = -x;return ;
}

#define maxn 100007
struct edge{
	int v,nxt;
}e[maxn<<1];
int head[maxn];
void add(int u,int v){e[++head[0]]={v,head[u]};head[u]=head[0];}


int main() {
}