Bellman-ford算法、SPFA算法求解最短路模板

///POJ 2387为例
#include
using namespace std;
const int maxn = 1e3 + 10;
const int INF  = 0x3f3f3f3f;
struct EdgeNode{ int from, to, w; };
EdgeNode Edge[maxn*maxn];
int Dis[maxn];
int N, M, cnt;

inline void init()
{
    for(int i=0; i<=N; i++)
        Dis[i] = INF;
    cnt = 0;
}

bool BellmanFord(int st)
{
    Dis[st] = 0;
    for(int i=0; i///N-1 次循环后肯定能找出最短路
        bool Changed = false;
        int to, from, weight;

        for(int j=0; j){
            to     = Edge[j].to,
            from   = Edge[j].from,
            weight = Edge[j].w;

            if(Dis[from]!=INF && Dis[to] > Dis[from] + weight){
                Changed = true;
                Dis[to] = Dis[from] + weight;
                ///pre[to] = j; //Record paths
            }
        }

        if(!Changed) return true;///如果没有边可以继续松弛了，说明算法结束且无负环
        if(i==N && Changed) return false;///有负环
    }
    return false; ///一般来说绝无可能执行到这一步
}

int main(void)
{
    while(~scanf("%d %d", &M, &N)){
        init();
        int from, to, weight;
        for(int i=0; i){
            scanf("%d %d %d", &from, &to, &weight);
            Edge[cnt].from = from;
            Edge[cnt].to   = to;
            Edge[cnt].w    = weight;
            cnt++;
            Edge[cnt].to   = from;
            Edge[cnt].from = to;
            Edge[cnt].w    = weight;
            cnt++;
        }
        BellmanFord(1);
        printf("%d\n", Dis[N]);
    }
    return 0;
}

///POJ 2387为例
#include 
#include 
#include 
#include 
#include <string.h>
using namespace std;

const int INF=0x3f3f3f3f;
const int maxn = 1e3 + 10;

struct EdgeNode{ int v, w, nxt; };
EdgeNode Edge[maxn*maxn];
bool vis[maxn];
int Head[maxn], Dis[maxn], cnt;
int N, M;
/// int PushCnt[maxn]; ///记录每一个节点的入队次数、方便判断负环

inline void init()
{
    for(int i=0; i<=N; i++)
        ///PushCnt[i] = 0;
        Head[i] = -1,
        Dis[i]  = INF,
        vis[i]  = false;
    cnt = 0;
}

inline void AddEdge(int from, int to, int weight)
{
    Edge[cnt].w = weight;
    Edge[cnt].v = to;
    Edge[cnt].nxt = Head[from];
    Head[from] = cnt++;
}

void SPFA(int st)///若要判断负环、改为 bool
{
    deque<int> que;
    que.push_back(st);
    vis[st]=true;
    Dis[st]=0;
    while (!que.empty())
    {
        int T=que.front(); que.pop_front();
        vis[T]=false;
        for (int i=Head[T]; i!=-1; i=Edge[i].nxt)
        {
            int v=Edge[i].v;
            int w=Edge[i].w;
            if (Dis[v]>Dis[T]+w){
                Dis[v]=Dis[T]+w;
                ///p[v] = T;
                if (!vis[v]){
                    ///if(++PushCnt[v] > N) return false; //有负环
                    vis[v]=true;
                    if(!que.empty() && Dis[v] < Dis[que.front()]) que.push_front(v);
                    else que.push_back(v);
                    //que.push_back(v); ///无SLF优化是这样写的
                }
            }
        }
    }
    /// return true;
}


int main(void)
{
    while(~scanf("%d %d", &M, &N)){
        init();
        int from, to, weight;
        for(int i=0; i){
            scanf("%d %d %d", &from, &to, &weight);
            AddEdge(from, to, weight);
            AddEdge(to, from, weight);
        }
        SPFA(1);
        printf("%d\n", Dis[N]);
    }
    return 0;
}