Shortest (vector + Dijkstra priority queue optimization)
#include<cstdio> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<stack> #include<set> #include<map> #include<vector> #include<cmath> #define Inf 0x3f3f3f3f const int maxn=1e5+5; typedef long long ll; using namespace std; struct node { int pos; int w; node (int x,int y) { pos=x; w=y; } bool friend operator < (node x,node y) { return x.w>y.w; } }; vector<node>vec[10005]; int dis[10005]; int vis[10005]; int n,m; void init() { for(int t=1;t<=n;t++) { dis[t]=Inf; } memset(vis,0,sizeof(vis)); } void Dijkstra(int s) { priority_queue<node>q; q.push(node(s,0)); dis[s]=0; while(!q.empty()) { node now=q.top(); q.pop(); if(vis[now.pos])continue; vis[now.pos]=1; for(int t=0;t<vec[now.pos].size();t++) { node to=vec[now.pos][t]; if(to.w+dis[now.pos]<dis[to.pos]) { dis[to.pos]=to.w+dis[now.pos]; to.w=dis[to.pos]; q.push(to); } } } } int main() { scanf("%d%d",&n,&m); init(); int u,v,w; for(int t=0;t<m;t++) { scanf("%d%d%d",&u,&v,&w); vec[u].push_back(node(v,w)); vec[v].push_back(node(u,w)); } Dijkstra(n); printf("%d\n",dis[1]); return 0; }
Optimization adjacency table queue + DIjkstra
#include<cstdio> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<stack> #include<set> #include<vector> #include<map> #include<cmath> #define Inf 0x3f3f3f3f const int maxn=1e5+5; typedef long long ll; using namespace std; struct edge { int u,v,w; int next; }Edge[10*maxn]; struct node { int pos,w; node(int x,int y) { pos=x; w=y; } bool friend operator < (node x,node y) { return x.w>y.w; } }; int head[1005],dis[1005],vis[1005],cnt=0; void add(int u,int v,int w) { Edge[cnt].u=u; Edge[cnt].v=v; Edge[cnt].w=w; Edge[cnt].next=head[u]; head[u]=cnt++; } void Dijkstra(int s) { dis[s]=0; priority_queue<node>q; q.push(node(s,0)); while(!q.empty()) { node now=q.top(); q.pop(); if(vis[now.pos])continue; vis[now.pos]=1; for(int i=head[now.pos];i!=-1;i=Edge[i].next) { if(dis[now.pos]+Edge[i].w<dis[Edge[i].v]) { dis[Edge[i].v]= dis[now.pos]+Edge[i].w; q.push(node(Edge[i].v,dis[Edge[i].v])); } } } return ; } int main() { int m,n; cin>>n>>m; int u,v,w; memset(head,-1,sizeof(head)); memset(dis,Inf,sizeof(dis)); for(int t=0;t<m;t++) { scanf("%d%d%d",&u,&v,&w); add(u,v,w); add(v,u,w); } Dijkstra(n); printf("%d\n",dis[1]); return 0; }
SPFA forfeit ring
#include<cstdio> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<stack> #include<set> #include<map> #include<vector> #include<cmath> #define Inf 0x3f3f3f3f const int maxn=1e5+5; typedef long long ll; using namespace std; struct Edge { int u,v,w; int next; }edge[7499]; int head[505],vis[505],cnt[505],dis[505],tot; void init() { memset(head,-1,sizeof(head)); memset(cnt,0,sizeof(cnt)); memset(vis,0,sizeof(vis)); memset(dis,Inf,sizeof(dis)); } void add(int u,int v,int w) { edge[tot].u=u; edge[tot].v=v; edge[tot].w=w; edge[tot].next=head[u]; head[u]=tot++; return; } int n,m,k; bool SPFA(int s) { dis[s]=0; cnt[s]=1; vis[s]=true; queue<int>q; q.push(s); while(!q.empty()) { int now=q.front(); q.pop(); vis[now]=false; for(int i=head[now];i!=-1;i=edge[i].next) { if(dis[now]+edge[i].w<dis[edge[i].v]) { dis[edge[i].v]= dis[now]+edge[i].w; int y=edge[i].v; cnt[y]=cnt[now]+1; if(cnt[y]>n) { return true; } if(vis[y]==false) { vis[y]=true; q.push(y); } } } } return false; } int main() { int T; cin>>T; while(T--) { tot=0; init(); scanf("%d%d%d",&n,&m,&k); int u,v,w; for(int t=0;t<m;t++) { scanf("%d%d%d",&u,&v,&w); add(u,v,w); add(v,u,w); } for(int t=0;t<k;t++) { scanf("%d%d%d",&u,&v,&w); add(u,v,-w); } if(SPFA(1)) { puts("YES"); } else { puts("NO"); } } }
Topological sorting sentenced ring
#include<cstdio> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<stack> #include<set> #include<vector> #include<map> #include<cmath> const int maxn=1e5+5; typedef long long ll; using namespace std; int du[105]; vector<int>vec[105]; int n,m; bool TPsort() { queue<int>q; int cnt=0; for(int t=0;t<n;t++) { if(du[t]==0) { q.push(t); } } while(!q.empty()) { int now=q.front(); q.pop(); cnt++; for(int t=0;t<vec[now].size();t++) { int nxt=vec[now][t]; du[nxt]--; if(du[nxt]==0) { q.push(nxt); } } } if(cnt!=n) { return false; } else { return true; } } int main() { while(scanf("%d%d",&n,&m)!=EOF) { if(n==0) { break; } memset(du,0,sizeof(du)); for(int t=0;t<n;t++) { vec[t].clear(); } int u,v; for(int t=0;t<m;t++) { scanf("%d%d",&u,&v); vec[u].push_back(v); du[v]++; } if(TPsort()) { puts("YES"); } else { puts("NO"); } } return 0; }
The diameter of the tree
#include<cstdio> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<stack> #include<set> #include<map> #include<vector> #define Inf 0x3f3f3f3f const int maxn=1e4+5; typedef long long ll; using namespace std; struct edge { int to,cost; }; vector<edge> e[maxn]; int farthest,ans; void dfs(int x,int pre,int dis) { for(int i=0;i<e[x].size();i++) { int xx = e[x][i].to; if(xx == pre) continue; dfs(xx,x,dis+e[x][i].cost); } if(dis > ans) { ans = dis; farthest = x; } } int main() { int i,j; int x,y; edge t; while(scanf("%d%d%d",&x,&y,&t.cost)!=EOF) { t.to = y; e[x].push_back(t); t.to = x; e[y].push_back(t); } ans = 0; dfs(1,-1,0); dfs(farthest,-1,0); printf("%d\n",years); return 0 ; }