这道题居然卡SPFA,难受,写了这么长时间的SPFA,都快把dij忘光了;
设d[i][j]为修j条路到i的最短距离,然后跑堆优化dij就行了;
实测中SPFA两组大数据超时严重;
dij约300ms一组大数据;
但是总感觉这个堆优化dij和SPFA好相像啊,奇怪;
1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<string> 5 #include<cstdlib> 6 #include<ctime> 7 #include<vector> 8 #include<algorithm> 9 #include<queue> 10 using namespace std; 11 #define LL long long 12 const int maxn=10010; 13 const int inf=1000000000; 14 struct node{ 15 int x,y,next; 16 int v; 17 }e[maxn*10]; 18 int linkk[maxn],len=0; 19 int n,m,k; 20 LL d[maxn][25]; 21 void insert(int x,int y,int v){ 22 e[++len].y=y; 23 e[len].x=x; 24 e[len].next=linkk[x]; 25 linkk[x]=len; 26 e[len].v=v; 27 } 28 void init(){ 29 scanf("%d%d%d",&n,&m,&k); 30 int x,y,v; 31 for(int i=1;i<=m;i++){ 32 scanf("%d%d%d",&x,&y,&v); 33 insert(x,y,v);insert(y,x,v); 34 } 35 } 36 struct bian{ 37 int x,k; 38 LL w; 39 bian(int a,int b,LL c){x=a,k=b,w=c;} 40 bool operator>(const bian& b)const{ 41 return w>b.w; 42 } 43 }; 44 priority_queue<bian,vector<bian>,greater<bian> > q; 45 void dij(){ 46 memset(d,10,sizeof(d)); 47 for(int i=0;i<=k;i++)d[1][i]=0; 48 q.push(bian(1,0,0)); 49 while(!q.empty()){ 50 bian tmp=q.top(); 51 q.pop(); 52 int x=tmp.x; 53 int p=tmp.k; 54 LL w=tmp.w; 55 for(int i=linkk[x];i;i=e[i].next){ 56 if(p<k&&w<d[e[i].y][p+1]){ 57 d[e[i].y][p+1]=w; 58 q.push(bian(e[i].y,p+1,w)); 59 } 60 if(w+e[i].v<d[e[i].y][p]){ 61 d[e[i].y][p]=w+e[i].v; 62 q.push(bian(e[i].y,p,d[e[i].y][p])); 63 } 64 } 65 } 66 } 67 void work(){ 68 dij(); 69 cout<<d[n][k]<<endl; 70 } 71 int main(){ 72 init(); 73 work(); 74 }