c++ spfa 链式前向星版本加上SLF优化版本的实现

普通版本

#include <iostream>
#include <queue>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <limits.h>
const int INF = 0x3f3f3f3f;
const int MAXN = 100010;
const int MAXM = 500050;
using namespace std;
struct Edge {
	int to, next, w;
	Edge(const int & _to = int(), const int & _next = int(), const int & _w = int()) : to(_to), next(_next), w(_w) {}
} edge[MAXM];
int dist[MAXN];
int visit[MAXN];
int head[MAXN];
int cnt;
void spfa(const int & st) {
	dist[st] = 0;
	queue<int> q;
	q.push(st);
	visit[st] = 1;
	while (!q.empty()) {
		int x = q.front();
		q.pop();
		visit[x] = 0;
		for (int i = head[x]; i;i = edge[i].next) {
			int y = edge[i].to;
			if (dist[y] > dist[x] + edge[i].w) {
				dist[y] = dist[x] + edge[i].w;
				if (!visit[y]) {
					q.push(y);
					visit[y] = 1;
				}
			}
		}
	}
}