Spfa模板

Spfa模板

#include<cstdio>
#include<queue> 
#include<cstring>
#define maxm 10005
#define maxn 105
#define INF 0x3f3f3f3f
using namespace std;

struct Edge{
	int to,cost,next;
}edge[maxm];

bool vis[maxn];
int dis[maxn],head[maxn],n,m,cnt;

void Init(){
	memset(vis,false,sizeof(vis));     //个人觉得用一个for来初始化时间复杂度更小 
	memset(head,-1,sizeof(head));      //head初始化为-1，cnt为0 
	cnt = 0;
	for(int i=1; i<=n; i++)
	    dis[i] = (i==1)? 0 : INF;
}

void add(int from,int to,int cost){
	edge[cnt].to = to;
	edge[cnt].cost = cost;
	edge[cnt].next = head[from];
	head[from] = cnt++;
}

void Spfa(int s){
	int u;
	queue<int> Q;
	Q.push(s);   //注意进队列 
	dis[s] = 0;
	vis[s] = true;
	while(!Q.empty()){
		u = Q.front();
		Q.pop();       //注意出队列 
		vis[u] = false;
		for(int i=head[u]; i!=-1; i=edge[i].next){
			int v = edge[i].to;
			int w = edge[i].cost;      //这两处的用i是指与U相连的边都进行松弛！ 
			if(dis[v] > dis[u] + w){
				dis[v] = dis[u] + w;
				if(!vis[v]){
					vis[v] = true;
					Q.push(v);     //注意进队列 
				}
			} 
		}
	}
}