2017-10-20 NOIP模拟赛

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int n,k,cnt;
char s[1000010];
int main(){
    freopen("trans.in","r",stdin);freopen("trans.out","w",stdout);
    //freopen("Cola.txt","r",stdin);
    while(scanf("%d%d",&n,&k)!=EOF){
        scanf("%s",s);cnt=0;
        int rest=0;
        for(int i=0;i<n;i++){
            if(s[i]==‘2‘&&s[i+1]==‘3‘){
                if(i>0&&(i+1)%2==0&&s[i-1]==‘2‘&&s[i+1]==‘3‘){
                    rest=k-cnt;break;
                }
                else if((i+1)%2==1&&s[i+1]==‘3‘&&s[i+2]==‘3‘){
                    rest=k-cnt;break;
                }
                else{
                    if((i+1)%2==0)s[i]=‘3‘;
                    else s[i+1]=‘2‘;
                    cnt++;
                    if(cnt==k)break;
                }
            }
        }
        rest%=2;
        if(rest==0||cnt==k){
            printf("%s\n",s);
        }
        else{
            for(int i=0;i<n;i++){
                if(s[i]==‘2‘&&s[i+1]==‘3‘){
                    if((i+1)%2==0)s[i]=‘3‘;
                    else s[i+1]=‘2‘;
                    break;
                }
            }
            printf("%s\n",s);
        }
    }
}

#include<iostream>
#include<cstdio>
#define maxn 210
using namespace std;
int n,m,map[maxn][7],num,ans,head[maxn],edge[maxn*6+10][maxn*6+10];
struct node{
    int to,pre,v;
}e[maxn*7*3];
int make_id(int i,int j){return (i-1)*5+j;}
void Insert(int from,int to,int v){
    e[++num].to=to;
    e[num].v=v;
    e[num].pre=head[from];
    head[from]=num;
    edge[from][to]=num;
}
void dfs(int x,int y,int sc,int len){
    if(x>n){
        ans=max(ans,sc);
        return;
    }
    int now=make_id(x,y);
    for(int i=head[now];i;i=e[i].pre){
        int to=e[i].to;
        if(e[i].v==0)continue;
        int xx=(to-1)/5+1,yy=to%5;
        if(yy==0)yy=5;
        e[i].v=0;
        if(map[xx][yy]>=0){
            int p=map[xx][yy];
            map[xx][yy]=0;
            dfs(xx,yy,sc,len+p);
            map[xx][yy]=p;
        }
        else {
            if(len+map[xx][yy]<0){ans=max(ans,sc);}
            else {
                int p=map[xx][yy];
                map[xx][yy]=0;
                dfs(xx,yy,sc-p,len+p);
                map[xx][yy]=p;
            }
        }
        e[i].v=1;
    }
}
int main(){
    freopen("snakevsblock.in","r",stdin);freopen("snakevsblock.out","w",stdout);
    //freopen("Cola.txt","r",stdin);
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=5;j++){
            int id=make_id(i,j);
            if(j!=1)Insert(id,make_id(i,j-1),1);//向左
            if(j!=5)Insert(id,make_id(i,j+1),1);//向右 
            Insert(id,make_id(i+1,j),1);//向下 
            scanf("%d",&map[i][j]);
        }
    scanf("%d",&m);
    int x,y;
    for(int i=1;i<=m;i++){
        scanf("%d%d",&x,&y);
        int id1=make_id(x,y),id2=make_id(x,y+1);
        e[edge[id1][id2]].v=0;
        e[edge[id2][id1]].v=0;
    }
    dfs(1,3,0,4);
    printf("%d",ans);
}

#include<iostream>
#include<cstring>
#include<cstdio>
#define maxn 100010
using namespace std;
int n,m,k,num,head[maxn],fa[maxn],dep[maxn],h[maxn],cnt;
bool vis[maxn],v[maxn];
int c[16][1<<15];
struct node{
    int to,pre;
}e[maxn*2];
struct Node{
    int l,r;
}p[300010];
void Insert(int from,int to){
    e[++num].to=to;
    e[num].pre=head[from];
    head[from]=num;
}
int count(int x){
    int res=0;
    while(x){
        if(x&1)res++;
        x>>=1;
    }
    return res;
}
void dfs(int now,int father){
    fa[now]=father;dep[now]=dep[father]+1;
    for(int i=head[now];i;i=e[i].pre){
        int to=e[i].to;
        if(to==father)continue;
        dfs(to,now);
    }
}
int sta;
bool lca(int a,int b){
    if(vis[a]||vis[b])return 1;
    if(dep[a]<dep[b])swap(a,b);
    while(dep[a]>dep[b]){
        a=fa[a];
        if(vis[a])return 1;
    }
    while(a!=b){
        a=fa[a];b=fa[b];
        if(vis[a]||vis[b])return 1;
    }
    return 0;
}
bool ok(int s){
    memset(vis,0,sizeof(vis));
    int pos=0;
    while(s){
        pos++;
        if(s&1)vis[h[pos]]=1;
        s>>=1;
    }
    for(int i=1;i<=k;i++){
        int a=p[i].l,b=p[i].r;
        if(lca(a,b))continue;
        else return 0;
    }
    return 1;
}
bool check(int x){
    for(int i=1;i<=c[x][0];i++){
        int s=c[x][i];
        if(ok(s)){
            sta=s;
            return 1;
        }
    }
    return 0;
}
int main(){
    freopen("ping.in","r",stdin);freopen("ping.out","w",stdout);
    //freopen("Cola.txt","r",stdin);
    scanf("%d%d",&n,&m);
    for(int i=0;i<=(1<<n)-1;i++){
        int nu=count(i);
        c[nu][++c[nu][0]]=i;
    }
    int x,y;
    for(int i=1;i<=m;i++){
        scanf("%d%d",&x,&y);
        Insert(x,y);Insert(y,x);
        if(!v[x])h[++cnt]=x,v[x]=1;
        if(!v[y])h[++cnt]=y,v[y]=1;
    }
    dfs(1,1);
    scanf("%d",&k);
    for(int i=1;i<=k;i++)
        scanf("%d%d",&p[i].l,&p[i].r);
    int l=1,r=cnt,ans=0;
    while(l<=r){
        int mid=(l+r)>>1;
        if(check(mid))ans=mid,r=mid-1;
        else l=mid+1;
    }
    printf("%d\n",ans);
    int pos=0;
    while(sta){
        pos++;
        if(sta&1)printf("%d ",h[pos]);
        sta>>=1;
    }
    return 0;
}