P4554 小明的游戏,P1744 采购特价商品(spfa)

Posted 2022-02-24 钟钟终

https://www.luogu.com.cn/problem/P4554
P4554 小明的游戏
spfa
从二维表中建图，本题根据题意若相邻的符号相同则赋值为0，不同则赋值为1，利用spfa求最短路

#include <bits/stdc++.h>
#define y1 y11
using namespace std;
const int maxn=6e6+5;
const int inf=0x3f3f3f3f;
char mp[505][505];
int n,m,head[maxn],cnt,x1,y1,x2,y2,dist[maxn];
int dx[4]=0,1,0,-1;
int dy[4]=-1,0,1,0;
bool vis[maxn];
struct node

    int  to,nxt,dis;
e[maxn];

void add(int from,int to,int dis)

    e[++cnt].to=to;
    e[cnt].dis=dis;
    e[cnt].nxt=head[from];
    head[from]=cnt;

queue<int>q;
void spfa(int u)

    memset(dist,inf,sizeof(dist));
    dist[u]=0;
    q.push(u);
    vis[u]=1;
    while(!q.empty())
    
        int x=q.front();q.pop();
        vis[x]=0;
        for(int i=head[x];~i;i=e[i].nxt)
        
            int y=e[i].to;
            if(dist[y]>dist[x]+e[i].dis)
            
                dist[y]=dist[x]+e[i].dis;
                if(!vis[y])
                
                    vis[y]=1;q.push(y);
                
            
        
    

int main()

    while(scanf("%d%d",&n,&m)&&n&&m)
    
        memset(head,-1,sizeof(head));
        memset(vis,0,sizeof(vis));
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
            cin>>mp[i][j];
        for(int i=1;i<=n;i++)
        
            for(int j=1;j<=m;j++)
            
                for(int k=0;k<4;k++)
                
                    int nx=i+dx[k],ny=j+dy[k];
                    if(nx<=0||nx>n||ny<=0||ny>m)
                        continue;
                    if(mp[nx][ny]==mp[i][j])
                    
                        add(i*m+j,nx*m+ny,0);
                    
                    else
                        add(i*m+j,nx*m+ny,1);
                
            
        
        scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
        x1+=1;y1+=1;x2+=1;y2+=1;
        spfa(x1*m+y1);
        cout<<dist[x2*m+y2]<<endl;
    
    return 0;

P1744 采购特价商品
spfa的模板题，距离稍微变形了一下
https://www.luogu.com.cn/problem/P1744

#include <bits/stdc++.h>
using namespace std;
const int maxn=1e5+5;
int n,m,s,t,a[maxn],b[maxn],head[maxn],cnt;
bool vis[maxn];
double dist[maxn];
struct node

    int  to,nxt;
    double dis;
e[maxn];
double dd(int x1,int y1,int x2,int y2)

    double tmp=sqrt((x1-x2)*(x1-x2)*1.0+(y1-y2)*(y1-y2)*1.0);
    //cout<<tmp<<endl;
    return tmp;

void add(int from,int to,double dis)

    e[++cnt].to=to;
    e[cnt].dis=dis;
    e[cnt].nxt=head[from];
    head[from]=cnt;

queue<int>q;
void spfa(int u)

    for(int i=1;i<=n;i++)
        dist[i]=1000000.00;
    dist[u]=0;
    q.push(u);vis[u]=1;
    while(!q.empty())
    
        int x=q.front();q.pop();
        vis[x]=0;
        for(int i=head[x];i;i=e[i].nxt)
        
            int y=e[i].to;
            if(dist[y]>dist[x]+e[i].dis)
            
                dist[y]=dist[x]+e[i].dis;
                if(!vis[y])
                
                    vis[y]=1;q.push(y);
                
            
        
    

int main()

    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        scanf("%d%d",&a[i],&b[i]);
    scanf("%d",&m);
    for(int i=1;i<=m;i++)
    
        int u,v;scanf("%d%d",&u,&v);
        add(u,v,dd(a[u],b[u],a[v],b[v]));
        add(v,u,dd(a[u],b[u],a[v],b[v]));
    
    scanf("%d%d",&s,&t);
    spfa(s);
    printf("%.2lf\\n",dist[t]);
    return 0;