迪杰斯特拉：
struct node{
int id,val;
node(int id,int val):id(id),val(val){}
bool operator < (const node &a)const{
return val>a.val;
}
};
void add(int x,int y,int z){
to[++now]=y;val[now]=z;nex[now]=head[x];head[x]=now;
to[++now]=x;val[now]=z;nex[now]=head[y];head[y]=now;
}
priority_queue<node> q;
void dijkstra(int st,int en){
for(int i=1;i<=n;i++)dis[i]=inf;
memset(vis,0,sizeof(vis));
q.push(node(st,0));dis[st]=0;
while(!q.empty()){
int idx=q.top().id;q.pop();
vis[idx]=1;
for(int i=head[idx];~i;i=e[i].nex){
if(vis[e[i].to])continue;
if(dis[idx]<dis[e[i].to]-e[i].val){
dis[e[i].to]=e[i].val+dis[idx];
q.push(node(e[i].to,dis[e[i].to]));
}
}
}
}
pair优化
vector<pill> v[N];
priority_queue<pill,vector<pill>,greater<pill> >Q;
int vis[N];
int dist[N];
int main(){
memset(dist,125,sizeof(dist));
int n=read(),m=read();
for(int i=1;i<=m;i++){
int a=read(),b=read(),c=read();
v[a].pb(mk(b,c));v[b].pb(mk(a,c));
}
Q.push(mk(0,1));dist[1]=0;
while(!Q.empty()){
int j=Q.top().second;Q.pop();
if(vis[j])continue;vis[j]=1;
for(int i=0;i<v[j].size();i++){
if(vis[v[j][i].first])continue;
if(dist[v[j][i].first]>dist[j]+v[j][i].second){
dist[v[j][i].first]=dist[j]+v[j][i].second;
Q.push(mk(dist[v[j][i].first],v[j][i].first));
}
}
}
printf("%d\n",dist[n]);
}
SPFA：
int spfa(int st,int en){
for(int i=1;i<=qiang;i++){
dist[i]=inf;
vis[i]=0;
}
queue<int> q;
dist[st]=0; vis[st]=1;
q.push(st);
while(!q.empty()){
int now=q.front(); q.pop();
vis[now]=0;
for(int i=head[now];~i;i=e[i].next){
int v=e[i].to,w=e[i].val;
if(dist[v]>dist[now]+w){
dist[v]=dist[now]+w;
if(!vis[v]){
vis[v]=1;
q.push(v);
}
}
}
}
if(dist[en]>=inf) return -1;
return dist[en];
}
二分图最大匹配：
int match[N];
bool vis[N];
int fin(int h){
for(int i=0;i<=n;i++){
if(vis[i]||!link[h][i])continue;
vis[i]=1;
if(match[i]==0||fin(match[i])){
match[i]=h;return 1;
}
}
return 0;
}
int main(){
memset(match,0,sizeof(match));
...
for(int i=1;i<=n;i++){
memset(vis,0,sizeof(vis));
if(fin(i))ans++;
}
}
拓扑排序字典序最小
int in_degree[509];
int M[509][509];
int vis[509];
int main(){
int n,m;
while(scanf("%d%d",&n,&m)!=EOF){
int ans[500],ar=0;
for(int i=1;i<=n;i++)in_degree[i]=0;
memset(M,0,sizeof(M));memset(vis,0,sizeof(vis));
while(m--){
int a,b;scanf("%d%d",&a,&b);
if(M[a][b]==0)in_degree[b]++;
M[a][b]=1;
}
priority_queue<int,vector<int>,greater<int> >Q;
for(int i=1;i<=n;i++)if(in_degree[i]==0){
Q.push(i);vis[i]=1;
}
while(!Q.empty()){
int t=Q.top();Q.pop();
ans[++ar]=t;
for(int i=1;i<=n;i++){
if(vis[i]||M[t][i]==0)continue;
in_degree[i]--;
if(in_degree[i]==0){
Q.push(i);vis[i]=1;
}
}
}
if(ar!=n){printf("no\n");continue;}
for(int i=1;i<=n;i++){
printf("%d",ans[i]);
if(i==n)printf("\n");
else printf(" ");
}
}
}
最小生成树
struct node{
int x,y,w;
bool operator<(const node & a)const{
return w<a.w;
}
}edge[200005];
int fa[200005];
int fi(int t)
{ return fa[t]==t?fa[t]:fa[t]=fi(fa[t]);
}
int main()
{ int n,m,ans;
while(scanf("%d%d",&n,&m)!=EOF)
{ ans=0;
for(int i=0;i<n;i++)fa[i]=i;
for(int i=0;i<m;i++)
{ int a,b,c;scanf("%d%d%d",&a,&b,&c);
edge[i].x=a;edge[i].y=b;edge[i].w=c;
}
sort(edge,edge+m);
for(int i=0;i<m;i++)
{ int m1=edge[i].x,m2=edge[i].y;
if(fi(m1)==fi(m2))continue;
ans+=edge[i].w;
fa[fi(m1)]=fi(m2);
}
cout<<ans<<endl;
}
}
强连通
int n,numque=0,head[N],cnt,dfn[N],low[N],now,belong[N];
queue<int> que[N];
stack<int> sa;
struct edge{
int next,to;
}e[N];
void add(int u,int v){
e[cnt].to=v,e[cnt].next=head[u];
head[u]=cnt++;
}
void init(){
memset(head,-1,sizeof(head));
memset(in,0,sizeof(in));
numque=0,cnt=0,now=0;
memset(dfn,0,sizeof(dfn));
memset(low,0,sizeof(low));
memset(belong,0,sizeof(belong));
while(!sa.empty()) sa.pop();
}
void tarjan(int x){
dfn[x]=low[x]=++now;
sa.push(x);
for(int i=head[x];~i;i=e[i].next){
int v=e[i].to;
if(!dfn[v]){
tarjan(v);
low[x]=min(low[x],low[v]);
}
else if(!belong[i]) low[x]=min(low[x],low[v]);
}
if(dfn[x]==low[x]){
numque++;
while(1){
int a=sa.top(); sa.pop();
belong[a]=numque;
que[numque].push(a);
if(a==x) break;
}
}
}
K短路
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
#define LL long long
const int MAXN = 1100;
const int MAXM = 11000;
const int INF = 1e18;
struct EdgeNode{
int to;
LL w;
int next;
}Edges[MAXM],Edges1[MAXM];
int Head[MAXN],Head1[MAXN];
struct Node{
int to;
LL g,f;
bool operator < (const Node &r) const
{
if(r.f == f)
return r.g < g;
return r.f < f;
}
};
int vis[MAXN];LL Dist[MAXN];
int A_Star(int start,int end,int N,int k){
Node e,ne;
int Cnt = 0;
priority_queue<Node> que;
if(start == end)
k++;
if(Dist[start] == INF)
return -1;
e.to = start;
e.g = 0;
e.f = e.g + Dist[e.to];
que.push(e);
while( !que.empty() ) {
e = que.top();
que.pop();
if(e.to == end)
Cnt++;
if(Cnt == k)
return e.g;
for(int i = Head[e.to]; i != -1; i = Edges[i].next) {
ne.to = Edges[i].to;
ne.g = e.g + Edges[i].w;
ne.f = ne.g + Dist[ne.to];
que.push(ne);
}
}
return -1;
}
void SPFA(int s,int N){
for(int i = 0; i <= N; ++i)
Dist[i] = INF;
memset(vis,0,sizeof(vis));
vis[s] = 1;
Dist[s] = 0;
queue<int> Q;
Q.push(s);
while( !Q.empty() ) {
int u = Q.front();
Q.pop();
vis[u] = 0;
for(int i = Head1[u]; i != -1; i = Edges1[i].next) {
int temp = Dist[u] + Edges1[i].w;
if(temp < Dist[Edges1[i].to]) {
Dist[Edges1[i].to] = temp;
if(!vis[Edges1[i].to]) {
vis[Edges1[i].to] = 1;
Q.push(Edges1[i].to);
}
}
}
}
}
int main(){
int N,M,u,v,s,t,k;LL LIM,w;
while(~scanf("%d%d",&N,&M)) {
memset(Edges,0,sizeof(Edges));
memset(Edges1,0,sizeof(Edges1));
memset(Head,-1,sizeof(Head));
memset(Head1,-1,sizeof(Head1));
scanf("%d%d%d%lld",&s,&t,&k,&LIM);
for(int i = 0; i < M; ++i) {
scanf("%d%d%lld",&u,&v,&w);
Edges[i].to = v;
Edges[i].w = w;
Edges[i].next = Head[u];
Head[u] = i;
Edges1[i].to = u;
Edges1[i].w = w;
Edges1[i].next = Head1[v];
Head1[v] = i;
}
SPFA(t,N);
LL ans = A_Star(s,t,N,k);
if(ans==-1||ans>LIM)printf("Whitesnake!\n");
else printf("yareyaredawa\n");
}
return 0;
}
最大流
const int Ni = 510;
const int MAX = 1<<26;
struct Edge{
int u,v,c;
int next;
}edge[20*Ni];
int n,m;
int edn;
int p[Ni];
int d[Ni];
int sp,tp;
void addedge(int u,int v,int c)
{
edge[edn].u=u; edge[edn].v=v; edge[edn].c=c;
edge[edn].next=p[u]; p[u]=edn++;
edge[edn].u=v; edge[edn].v=u; edge[edn].c=0;
edge[edn].next=p[v]; p[v]=edn++;
}
int bfs()
{
queue <int> q;
memset(d,-1,sizeof(d));
d[sp]=0;
q.push(sp);
while(!q.empty())
{
int cur=q.front();
q.pop();
for(int i=p[cur];i!=-1;i=edge[i].next)
{
int u=edge[i].v;
if(d[u]==-1 && edge[i].c>0)
{
d[u]=d[cur]+1;
q.push(u);
}
}
}
return d[tp] != -1;
}
int dfs(int a,int b)
{
int r=0;
if(a==tp)return b;
for(int i=p[a];i!=-1 && r<b;i=edge[i].next)
{
int u=edge[i].v;
if(edge[i].c>0 && d[u]==d[a]+1)
{
int x=min(edge[i].c,b-r);
x=dfs(u,x);
r+=x;
edge[i].c-=x;
edge[i^1].c+=x;
}
}
if(!r)d[a]=-2;
return r;
}
int dinic(int sp,int tp)
{
int total=0,t;
while(bfs())
{
while(t=dfs(sp,MAX))
total+=t;
}
return total;
}
int main()
{
sp=402,tp=401;
int i,u,v,c;
int a,b;
scanf("%d%d%d",&n,&a,&b);
edn=0;
memset(p,-1,sizeof(p));
for(int i=1;i<=a;i++)addedge(402,i,1);
for(int i=1;i<=b;i++)addedge(i+300,401,1);
for(int i=1;i<=n;i++)addedge(i+100,i+200,1);
for(i=1;i<=n;i++){
int x,y;
scanf("%d%d",&x,&y);
while(x--){
int tmp;
scanf("%d",&tmp);
addedge(tmp,i+100,1);
}
while(y--){
int tmp;
scanf("%d",&tmp);
addedge(i+200,tmp+300,1);
}
}
printf("%d\n",dinic(402,401));
return 0;
}