洛谷 P2439 [SDOI2005]阶梯教室设备利用

题目连接

简单sort+dp，类比区间覆盖

#include<cstdio>#include<iostream>#include<algorithm>using namespace std;struct data{    int x,y;}a[100005];int dp[100005];inline bool cmp(data a,data b){    return a.y<b.y;}inline void read(int &res){    static char ch;register int flag=1;    while((ch=getchar())<'0'||ch>'9')if(ch=='-')flag=-1;res=ch-48;    while((ch=getchar())>='0'&&ch<='9')res=res*10+ch-48;res*=flag;}int n,k=1;int main(){    freopen("rez.in","r",stdin);    freopen("rez.out","w",stdout);    read(n);    for(register int i=1;i<=n;i++)        read(a[i].x),read(a[i].y);    sort(a+1,a+1+n,cmp);    for(register int i=1;i<=a[n].y;i++){        dp[i]=dp[i-1];        for(;a[k].y<=i&&k<=n;k++)            dp[i]=max(dp[i],dp[a[k].x]-1+a[k].y-a[k].x+1);    }    printf("%d\n",dp[a[n].y]);    return 0;}