题目：Castle Defense
思路：
二分+贪心。注意LL的应用。
数据生成器：
#include<bits/stdc++.h>
using namespace std;#define maxn 5
#define maxr 5
#define maxk 5
#define Rand() (rand()+rand()%19260817)int n,r,k;int main() {srand(time(NULL));n=Rand()%maxn+1;r=Rand()%maxr+1;k=Rand()%maxk;printf("%d %d %d\n",n,r,k);for(int i=1;i<=n;i++) printf("%d ",Rand()%maxk+1);return 0;
}代码：
#include<bits/stdc++.h>
using namespace std;#define maxn 500000
#define ll long long
#define inf ((1LL)<<60)ll n,r,k;
ll a[maxn*3+5],c[maxn*3+5];
ll tg[maxn*3+5];bool judge(ll x) {memset(tg,0,sizeof(tg));ll s=0,b=0;for(int i=1;i<=n;i++) {b+=a[i];b-=tg[i];if(b<x) {ll y=x-b;tg[i+2*r+1]+=y;b+=y;s+=y;}if(s>k) return 0;}return 1;
}ll binsearch(){ll l=0,r=inf;while(l+1<r) {ll mid=l+(r-l)/2;if(judge(mid)) l=mid;else r=mid;}if(judge(l+1)) return l+1;if(!judge(l)) return l-1;else return l;
}int main(){scanf("%lld%lld%lld",&n,&r,&k);for(int i=1;i<=n;i++) scanf("%lld",&c[i]);for(int i=1;i<=n;i++) {if(i>r) a[i-r]+=c[i];else a[1]+=c[i];a[i+r+1]-=c[i];}ll ans=binsearch();if(ans<0) ans=0;printf("%lld",ans);return 0;
}