bzoj2100 [Usaco2010 Dec]Apple Delivery（slf优化的spfa）

朴素spfa过不去啊啊啊。。。所谓slf优化，就是small label first策略，设要加入的节点是j，队首元素为i，若dist(j) < dist(i)，则将j插入队首，否则插入队尾。 我们用双端队列deque来实现就好了。
还有一种更高效的LLL优化：Large Label Last 策略，设队首元素为i，队列中所有dist值的平均值为x，若dist(i)>x则将i插入到队尾，查找下一元素，直到找到某一i使得dist(i)<=x，则将i出对进行松弛操作。

slf优化

#include <bits/stdc++.h>using namespace std;#define N 100010#define M 200010#define inf 0x3f3f3f3f#define ll long longinline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,s,t1,t2,d[N],h[N],num=0;bool inq[N];struct edge{    int to,next,val;}data[M<<1];inline void add1(int x,int y,int val){    data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=val;}void spfa(int ss){    deque<int>q;memset(d,0x3f,sizeof(d));    q.push_back(ss);d[ss]=0;inq[ss]=1;    while(!q.empty()){        int x=q.front();q.pop_front();inq[x]=0;        for(int i=h[x];i;i=data[i].next){            int y=data[i].to;            if(d[x]+data[i].val<d[y]){                d[y]=d[x]+data[i].val;                if(!inq[y]){                    inq[y]=1;                    if(!q.empty()&&d[y]<d[q.front()]) q.push_front(y);                    else q.push_back(y);                }            }        }    }}int main(){//  freopen("a.in","r",stdin);    m=read();n=read();s=read();t1=read();t2=read();    while(m--){        int x=read(),y=read(),val=read();add1(x,y,val);add1(y,x,val);    }    spfa(t1);    int ans=d[s]+d[t2];    spfa(t2);    printf("%d\n",min(ans,d[s]+d[t1]));    return 0;}

lll优化+slf优化

#include <bits/stdc++.h>using namespace std;#define N 100010#define M 200010#define inf 0x3f3f3f3f#define ll long longinline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,s,t1,t2,d[N],h[N],num=0;bool inq[N];struct edge{    int to,next,val;}data[M<<1];inline void add1(int x,int y,int val){    data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=val;}void spfa(int ss){    deque<int>q;memset(d,0x3f,sizeof(d));    q.push_back(ss);d[ss]=0;inq[ss]=1;int tot=1,sum=0;    while(!q.empty()){        int x=q.front();q.pop_front();        if(d[x]*tot>sum){q.push_back(x);continue;}//lll优化         tot--;sum-=d[x];inq[x]=0;        for(int i=h[x];i;i=data[i].next){            int y=data[i].to;            if(d[x]+data[i].val<d[y]){                d[y]=d[x]+data[i].val;                if(!inq[y]){                    inq[y]=1;tot++;sum+=d[y];//slf优化                     if(!q.empty()&&d[y]<d[q.front()]) q.push_front(y);                    else q.push_back(y);                }            }        }    }}int main(){//  freopen("a.in","r",stdin);    m=read();n=read();s=read();t1=read();t2=read();    while(m--){        int x=read(),y=read(),val=read();add1(x,y,val);add1(y,x,val);    }    spfa(t1);    int ans=d[s]+d[t2];    spfa(t2);    printf("%d\n",min(ans,d[s]+d[t1]));    return 0;}