Atcoder regular Contest 073(C - Sentou)

Atcoder regular Contest 073(C - Sentou)

传送门

每个人对开关的影响区间为a[i]--a[i]+t,因此此题即为将所有区间离散化后求所有独立区间的长度和

#include<queue>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define ll long long
#define inf 1000000000LL
#define mod 1000000007
using namespace std;
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;
}
const int N=2e5+10;
pair<ll,ll> B[N*2];
int main()
{
   // while(true)
    {
        int n=read(),t=read();
        int top=0;
        ll x;
        for(int i=0;i<n;i++)
        {
            x=read();
            B[top].first=x;
            B[top].second=-1;
            top++;
           // cout<<x+t<<endl;
            B[top].first=x+t;
            B[top].second=1;
            top++;
        }
        sort(B,B+top);
        int count=0;
        ll pre=0,ans=0;
        bool first=1;
        for(int i=0;i<top;i++)
        {
            if(B[i].second==1){
                count++;
                if(count==0){
                    ans+=B[i].first-pre;
                }
            }
            if(B[i].second==-1){
                count--;
                if(count==-1){
                    pre=B[i].first;
                }
            }
        }
        printf("%I64d\n",ans);
    }
    return 0;
}