poj2373 Dividing the Path (单调队列+dp）

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #define inf 0x3f3f3f3f
 5 using namespace std;
 6 const int maxl=1000010;
 7 
 8 int rd(){
 9     int x=0,neg=1;char c=getchar();
10     while(c<‘0‘||c>‘9‘) {if(c==‘-‘) neg=-1;c=getchar();}
11     while(c>=‘0‘&&c<=‘9‘) x=x*10+c-‘0‘,c=getchar();
12     return x*neg;
13 }
14 
15 int N,L,A,B;
16 int f[maxl];
17 int lll[maxl],q[maxl][2],qh,qt;
18 bool flag[maxl];
19 
20 inline void insert(int x,int y){
21     for(int i=qt;i>=qh;i--){
22         if(q[x][0]<x){
23             qt=i+1;q[qt][0]=x;q[qt][1]=y;return;
24         } 
25     }qt=qh;q[qt][0]=x;q[qt][1]=y;
26 }
27 
28 int main(){
29     //freopen("2373.in","r",stdin);
30     int i,j,k,ans=inf;
31     N=rd();L=rd();A=rd();B=rd();
32     for(i=1;i<=N;i++){
33         j=rd();k=rd();
34         if(j+1<k){
35             lll[j+1]++;lll[k]--;
36         }
37     }for(i=1,j=0;i<L;i++){
38         j+=lll[i];if(j>0||i%2==1) flag[i]=1;
39     }
40     qt=qh=1;memset(f,-1,sizeof(f));
41     for(i=2*A;i<=2*B;i++){
42         if(!flag[i]) f[i]=1;
43     }
44     for(i=2*A;i+2*A<=L;i++){
45         if(!flag[i]&&f[i]!=-1){
46             insert(f[i],i);
47         }while(i-q[qh][1]>2*B-2*A&&qh<=qt) qh++;
48         if(!q[qh][1]||flag[i+2*A]) continue;
49         if(i+2*A==L) ans=q[qh][0]+1;
50         else f[i+2*A]=q[qh][0]+1;
51     }
52     if(ans!=inf) printf("%d",ans);
53     else printf("-1");
54 }