做题记录 Luogu P3371

标签：target   std   单源最短路   printf   规划   mem   ble   using   差分   

Luogu P3371 【模板】单源最短路径（弱化版）

练习一下那个死了的算法（最近好多东西要用到啊：分数规划、差分约束...）

#include<bits/stdc++.h>
using namespace std;
#define N 1000005
int first[N], Next[N], to[N], w[N], tot;
int dis[N], vis[N], cnt[N], n, m, s;
void add(int x, int y, int z)
{
	Next[++tot] = first[x];
	first[x] = tot;
	to[tot] = y;
	w[tot] = z;
	return;
}
int spfa(int x)
{
	deque<int> q;
	memset(dis, 0x3f, sizeof(dis));
	memset(vis, 0, sizeof(vis));
	memset(cnt, 0, sizeof(cnt));
	dis[x] = 0;
	vis[x] = 1;
	q.push_front(x);
	while(!q.empty())
	{
		int u = q.front();
		q.pop_front();
		vis[u] = 0;
		for(int i = first[u]; i; i = Next[i])
		{
			int v = to[i];
			if(dis[u] + w[i] < dis[v])
			{
				dis[v] = dis[u] + w[i];
				if(!vis[v])
				{
					if(++cnt[v] >= n)
					{
						return 0;
					}
					vis[v] = 1;
					if(q.empty() || dis[v] < dis[q.front()])
					{
						q.push_front(v);
					}
					else
					{
						q.push_back(v);
					}
				}
			}
		}
	}
	return 1;
}
int main()
{
	scanf("%d%d%d", &n, &m, &s);
	int u, v, w;
	for(int i = 1; i <= m; i++)
	{
		scanf("%d%d%d", &u, &v, &w);
		add(u, v, w);
	}
	if(!spfa(s))
	{
		printf("This graph has got wrong!");
		return 0;
	}
	for(int i = 1; i <= n; i++)
	{
		printf("%d ", (dis[i] == 0x3f3f3f3f ? 2147483647 : dis[i]));
	}
	return 0;
}

做题记录 Luogu P3371

标签：target   std   单源最短路   printf   规划   mem   ble   using   差分   

原文地址：https://www.cnblogs.com/fanypcd/p/14940618.html