noip2017普及题解

https://www.luogu.org/problemnew/show/3954

https://www.luogu.org/problemnew/show/3955

https://www.luogu.org/problemnew/show/3956

https://www.luogu.org/problemnew/show/3957

T1

甚至不想用c++写

a,b,c=map(int,input().split(' '))
print((a+a+b+b+b+c+c+c+c+c)//10)

T2

乱水

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cctype>
#define rg register
#define il inline
#define vd void
il int gi(){
rg int x=0;rg bool flg=0;rg char ch=getchar();
while(!isdigit(ch)){if(ch=='-')flg=1;ch=getchar();}
while(isdigit(ch))x=x*10-'0'+ch,ch=getchar();
return flg?-x:x;
}
int ans[10000001];
il vd checkmn(int&a,int b){if(b<a)a=b;}
int main(){
//  freopen("librarian.in","r",stdin);
//  freopen("librarian.out","w",stdout);
int n=gi(),orz,q=gi();
for(rg int i=0;i<10000001;++i)ans[i]=19260817;
while(n--){
orz=gi();
checkmn(ans[orz],orz);
checkmn(ans[orz%10000000],orz);
checkmn(ans[orz%1000000],orz);
checkmn(ans[orz%100000],orz);
checkmn(ans[orz%10000],orz);
checkmn(ans[orz%1000],orz);
checkmn(ans[orz%100],orz);
checkmn(ans[orz%10],orz);
}
for(rg int i=0;i<10000001;++i)if(ans[i]==19260817)ans[i]=-1;
while(q--)gi(),orz=gi(),printf("%d\n",ans[orz]);
return 0;
}

T3

dij

还有BFS/SPFA/DFS/DP...

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cctype>
#include<queue>
#include<cstring>
#define rg register
#define il inline
#define vd void
il int gi(){
rg int x=0;rg bool flg=0;rg char ch=getchar();
while(!isdigit(ch)){if(ch=='-')flg=1;ch=getchar();}
while(isdigit(ch))x=x*10-'0'+ch,ch=getchar();
return flg?-x:x;
}
const int maxn=101;
int col[maxn][maxn];
struct orzyyb{int x,y;bool col;};
int f[maxn][maxn][2];
bool vis[maxn][maxn][2];
il bool operator <(const orzyyb&a,const orzyyb&b){return f[a.x][a.y][a.col]>f[b.x][b.y][b.col];}
std::priority_queue<orzyyb>que;
const int X[]={0,0,0,1,-1},Y[]={0,1,-1,0,0};
int main(){
//  freopen("chess.in","r",stdin);
//  freopen("chess.out","w",stdout);
int n=gi(),m=gi();
int x,y,xx,yy,c;
memset(col,-1,sizeof col);
memset(f,63,sizeof f);
while(m--)x=gi(),y=gi(),col[x][y]=gi();
que.push((orzyyb){1,1,(bool)col[1][1]});
f[1][1][col[1][1]]=0;
orzyyb p;
while(!que.empty()){
p=que.top();que.pop();
x=p.x,y=p.y,c=p.col;
if(vis[x][y][c])continue;
vis[x][y][c]=1;
for(rg int i=1;i<5;++i){
xx=x+X[i],yy=y+Y[i];
if(xx<1||xx>n||yy<1||yy>n)continue;
if(~col[xx][yy]){
if(f[xx][yy][col[xx][yy]]>f[x][y][c]+(c^col[xx][yy])){
f[xx][yy][col[xx][yy]]=f[x][y][c]+(c^col[xx][yy]);
que.push((orzyyb){xx,yy,(bool)col[xx][yy]});
}
}else if(~col[x][y]){
if(f[xx][yy][0]>f[x][y][c]+(c^0)+2){
f[xx][yy][0]=f[x][y][c]+(c^0)+2;
que.push((orzyyb){xx,yy,0});
}
if(f[xx][yy][1]>f[x][y][c]+(c^1)+2){
f[xx][yy][1]=f[x][y][c]+(c^1)+2;
que.push((orzyyb){xx,yy,1});
}
}
}
}
int ans=std::min(f

[0],f

[1]);
if(ans==1061109567)ans=-1;
printf("%d\n",ans);
return 0;
}

T4

太套路了

显然答案单调，所以二分k

check用动态规划

一个状态到下一个状态，转移过来的区间会右移（不会左移），所以单调队列优化

套路的死

PS.check加个优化快一倍

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cctype>
#define rg register
#define il inline
#define vd void
typedef int mainint;
#define int long long
il int gi(){
rg int x=0;rg bool flg=0;rg char ch=getchar();
while(!isdigit(ch)){if(ch=='-')flg=1;ch=getchar();}
while(isdigit(ch))x=x*10-'0'+ch,ch=getchar();
return flg?-x:x;
}
const int maxn=500010;
int n,x[maxn],s[maxn];
il bool dp(int l,int r,int k){
--k;
static int f[maxn],que[maxn];
int hd=0,tl=0,q=1,ret=-1e18;
for(rg int i=1;i<=n;++i){
while(x[i]-x[q]>=l){
while((hd^tl)&&f[que[tl-1]]<=f[q])--tl;
que[tl++]=q++;
}
while((hd^tl)&&x[i]-x[que[hd]]>r)++hd;
if(x[i]>=l&&x[i]<=r)f[i]=s[i];
else f[i]=-1e18;
if(hd^tl)f[i]=std::max(f[i],f[que[hd]]+s[i]);
if(f[i]>k)return 0;
}
return 1;
}
mainint main(){
//  freopen("jump.in","r",stdin);
//  freopen("jump.out","w",stdout);
n=gi();
int d=gi(),k=gi();
for(rg int i=1;i<=n;++i)x[i]=gi(),s[i]=gi();
if(dp(1,x
,k)){puts("-1");return 0;}
int l=0,r=x
,mid;
while(l<r){
mid=(l+r)>>1;
if(dp(std::max(1ll,d-mid),std::min(d+mid,x
),k))l=mid+1;
else r=mid;
}
printf("%lld\n",l);
return 0;
}