1290A

Link

Solution:

O(n2):

#include <bits/stdc++.h>
# define LL long long
using namespace std;
const int INF=0x7fffffff;
int n, m, k;
int arr[3510];
int b[3510];
int main(){
    int T;
    scanf("%d", &T);
    while(T--){
        scanf("%d %d %d", &n, &m, &k);
        for(int i=1;i<=n;++i){
            scanf("%d", arr+i);
        }

        k=min(k,m-1);
        for(int i=0;i<=m-1;++i){
            b[i]=max(arr[i+1],arr[i+1+n-m]);
        }

        int ans=0;
        for(int x=0;x<=k;++x){
            int localmin=INF;
            for(int xaddy=x;xaddy<=x+m-1-k;++xaddy){
                localmin=min(localmin,b[xaddy]);
            }
            ans=max(ans,localmin);
        }
        printf("%d
", ans);
    }
    return 0;
}

Segment Tree:

#include <bits/stdc++.h>
# define LL long long
using namespace std;
const int INF=0x7fffffff;
int n, m, k;
int arr[3510];
int b[3510];
int seg[3510<<2];

void build(int idx, int left, int right){
    if(left==right){
        seg[idx]=b[left];
        return;
    }
    int mid=(left+right)>>1;
    build(idx*2+1,left,mid);
    build(idx*2+2,mid+1,right);
    seg[idx]=min(seg[idx*2+1],seg[idx*2+2]);
}

int query(int idx, int qleft, int qright, int left, int right){
    if(qleft>right || qright<left) return INF;
    if(qleft<=left && qright>=right){
        return seg[idx];
    }

    int mid=(left+right)>>1;
    int res=INF;
    int t1=query(idx*2+1,qleft,qright,left,mid);
    int t2=query(idx*2+2,qleft,qright,mid+1,right);
    res=min(res,min(t1,t2));
    return res;
}

int main(){
    int T;
    scanf("%d", &T);
    while(T--){
        memset(seg,127,sizeof(seg));
        scanf("%d %d %d", &n, &m, &k);
        for(int i=1;i<=n;++i){
            scanf("%d", arr+i);
        }

        k=min(k,m-1);
        for(int i=0;i<=m-1;++i){
            b[i]=max(arr[i+1],arr[i+1+n-m]);
        }
        build(0,0,m-1);
        int ans=0;
        int xaddy=0;
        for(int x=0;x<=k;++x){
            int localmin=query(0,x,x+m-1-k, 0,m-1);
            ans=max(ans,localmin);
        }
        printf("%d
", ans);
    }
    return 0;
}

Deque:

#include <bits/stdc++.h>
# define LL long long
using namespace std;
const int INF=0x7fffffff;
int n, m, k;
int arr[3510];
int b[3510];
int main(){
    int T;
    scanf("%d", &T);
    while(T--){
        scanf("%d %d %d", &n, &m, &k);
        for(int i=1;i<=n;++i){
            scanf("%d", arr+i);
        }

        k=min(k,m-1);
        for(int i=0;i<=m-1;++i){
            b[i]=max(arr[i+1],arr[i+1+n-m]);
        }
        deque<int> q;
        int ans=0;
        int xaddy=0;
        for(int x=0;x<=k;++x){
            while(q.size()>0 && q.front()<x) q.pop_front();

            while(xaddy<=x+m-1-k){
                while(q.size()>0 && b[xaddy]<=b[q.back()]){
                    q.pop_back();
                }
                q.push_back(xaddy);
                ++xaddy;
            }
            ans=max(ans,b[q.front()]);
        }
        printf("%d
", ans);
    }
    return 0;
}