NOIP模拟10.24 R2

2015提高D2
A.跳石头。二分答案+贪心 AC
B.子串。dp。写过一遍的。。结果用了另一种方法写过的。。AC
C.运输计划。拿了60的暴力分。正解待更新。
upd：C正解看这里：传送门

A

#include <bits/stdc++.h>using namespace std;#define ll long long#define N 50010#define inf 0x3f3f3f3finline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,d[N],l=1,r;inline bool jud(int x){    int last=0,res=0;    for(int i=1;i<=n;++i){        if(last+x<=d[i]) last=d[i];else res++;    }return res<=m;}int main(){//  freopen("a.in","r",stdin);    r=read();n=read();m=read();    for(int i=1;i<=n;++i) d[i]=read();d[++n]=r;    while(l<=r){        int mid=l+r>>1;        if(jud(mid)) l=mid+1;else r=mid-1;    }printf("%d\n",l-1);    return 0;}

B

#include <bits/stdc++.h>using namespace std;#define ll long long#define N 1010#define M 210#define inf 0x3f3f3f3f#define mod 1000000007inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,kk,dp[2][M][M],f[2][M][M],p=0;//dp[i][j][k] a的前i个字符，匹配到b[j]，分为k段的方案数,f[i][j][k] 要求a[i]==b[j]的方案数char a[N],b[M];int main(){//  freopen("a.in","r",stdin);    n=read();m=read();kk=read();    scanf("%s%s",a+1,b+1);dp[0][0][0]=dp[1][0][0]=1;    for(int i=1;i<=n;++i){        for(int j=1;j<=m;++j)            for(int k=1;k<=kk;++k){                dp[p^1][j][k]=dp[p][j][k];f[p^1][j][k]=0;                if(a[i]!=b[j]) continue;                f[p^1][j][k]=(dp[p][j-1][k-1]+f[p][j-1][k])%mod;                dp[p^1][j][k]=(dp[p^1][j][k]+f[p^1][j][k])%mod;            }p^=1;    }printf("%d\n",dp[p][m][kk]);    return 0;}

C

60分版。

#include <bits/stdc++.h>using namespace std;#define ll long long#define N 300010#define inf 0x3f3f3f3finline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,h[N],num=0,dep[N],fa[N][20],sum[N][20],mx[N][20],Log[N],w[N];int len[N],ans=0;struct edge{    int to,next,val;}data[N<<1];vector<int>a[N];void dfs(int x){    for(int i=1;i<=Log[n];++i){        if(!fa[x][i-1]) continue;        fa[x][i]=fa[fa[x][i-1]][i-1];        sum[x][i]=sum[x][i-1]+sum[fa[x][i-1]][i-1];        mx[x][i]=max(mx[x][i-1],mx[fa[x][i-1]][i-1]);    }    for(int i=h[x];i;i=data[i].next){        int y=data[i].to;if(y==fa[x][0]) continue;        fa[y][0]=x;dep[y]=dep[x]+1;sum[y][0]=data[i].val;        mx[y][0]=data[i].val;w[y]=data[i].val;dfs(y);    }}void solve0(){    int x=read(),y=read(),mxx=0,summ=0;    if(dep[x]<dep[y]) swap(x,y);    int t=dep[x]-dep[y];    for(int i=Log[t];i>=0;--i)        if(t&(1<<i)) mxx=max(mxx,mx[x][i]),summ+=sum[x][i],x=fa[x][i];    if(x==y){printf("%d\n",summ-mxx);return;}    for(int i=Log[n];i>=0;--i){        if(fa[x][i]==fa[y][i]) continue;        mxx=max(mxx,max(mx[x][i],mx[y][i]));summ+=sum[x][i]+sum[y][i];        x=fa[x][i],y=fa[y][i];    }mxx=max(mxx,max(mx[x][0],mx[y][0]));summ+=sum[x][0]+sum[y][0];    printf("%d\n",summ-mxx);return;}inline int lca(int x,int y){    if(dep[x]<dep[y]) swap(x,y);    int t=dep[x]-dep[y];    for(int i=Log[t];i>=0;--i)        if(t&(1<<i)) x=fa[x][i];    if(x==y) return x;    for(int i=Log[n];i>=0;--i)        if(fa[x][i]!=fa[y][i]) x=fa[x][i],y=fa[y][i];    return fa[x][0];}int main(){//  freopen("a.in","r",stdin);    n=read();m=read();Log[0]=-1;    for(int i=1;i<=n;++i) Log[i]=Log[i>>1]+1;    for(int i=1;i<n;++i){        int x=read(),y=read(),v=read();        data[++num].to=x;data[num].next=h[y];h[y]=num;data[num].val=v;        data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=v;    }dfs(1);if(m==1){solve0();return 0;}    for(int i=1;i<=m;++i){        int x=read(),y=read(),t=lca(x,y);        while(x!=t) a[x].push_back(i),len[i]+=w[x],x=fa[x][0];        while(y!=t) a[y].push_back(i),len[i]+=w[y],y=fa[y][0];ans=max(ans,len[i]);    }for(int i=2;i<=n;++i){        int res=0;        for(int j=0;j<a[i].size();++j) len[a[i][j]]-=w[i];        for(int j=1;j<=m;++j) res=max(res,len[j]);ans=min(ans,res);        for(int j=0;j<a[i].size();++j) len[a[i][j]]+=w[i];    }printf("%d\n",ans);    return 0;}

正解

#include <bits/stdc++.h>using namespace std;#define ll long long#define inf 0x3f3f3f3f#define N 300010inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,h[N],num=0,fa[N][20],dep[N],dis[N],w[N],Log[N];int mid,cnt,c[N];bool flag;struct edge{    int to,next,val;}data[N<<1];struct Data{    int u,v,t,len;}a[N];inline bool cmp(Data x,Data y){    return x.len>y.len;}void dfs(int x){    for(int i=1;i<=Log[n];++i){        if(!fa[x][i-1]) continue;        fa[x][i]=fa[fa[x][i-1]][i-1];    }    for(int i=h[x];i;i=data[i].next){        int y=data[i].to;if(y==fa[x][0]) continue;        fa[y][0]=x;dep[y]=dep[x]+1;w[y]=data[i].val;        dis[y]=dis[x]+w[y];dfs(y);    }}inline int lca(int x,int y){    if(dep[x]<dep[y]) swap(x,y);    int t=dep[x]-dep[y];    for(int i=Log[t];i>=0;--i)        if(t&(1<<i)) x=fa[x][i];    if(x==y) return x;    for(int i=Log[n];i>=0;--i)        if(fa[x][i]!=fa[y][i]) x=fa[x][i],y=fa[y][i];    return fa[x][0];}int calc(int x){    int res=c[x];    for(int i=h[x];i;i=data[i].next){        int y=data[i].to;if(y==fa[x][0]) continue;        res+=calc(y);if(flag) return res;    }if(res!=cnt) return res;    if(a[1].len-w[x]<=mid) flag=1;return res;}bool jud(){    cnt=0;memset(c,0,sizeof(c));flag=0;    for(int i=1;i<=m;++i){        if(a[i].len<=mid) break;cnt++;        c[a[i].u]++;c[a[i].v]++;c[a[i].t]-=2;    }calc(1);return flag;}int main(){//  freopen("a.in","r",stdin);    n=read();m=read();Log[0]=-1;    for(int i=1;i<=n;++i) Log[i]=Log[i>>1]+1;    for(int i=1;i<n;++i){        int x=read(),y=read(),v=read();        data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=v;        data[++num].to=x;data[num].next=h[y];h[y]=num;data[num].val=v;    }dfs(1);    for(int i=1;i<=m;++i){        a[i].u=read();a[i].v=read();a[i].t=lca(a[i].u,a[i].v);        a[i].len=dis[a[i].u]+dis[a[i].v]-2*dis[a[i].t];    }sort(a+1,a+m+1,cmp);    int l=0,r=a[1].len;    while(l<=r){        mid=l+r>>1;        if(jud()) r=mid-1;else l=mid+1;    }printf("%d\n",r+1);    return 0;}