RMQ问题

Posted 2020-12-04 sun123zxy

现给你n（<=1000000）个整数（都小于longint）,有k(0< k<= 1000000)个询问,对于每个询问（Ｌ，Ｒ），回答(L,R)内的最大值为多少？

 

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;

const int MAXARR=1000005;
const int MAXLOG=(int)log2(MAXARR)+5;

int n,askn;
int dp[MAXARR][MAXLOG];
int a[MAXARR];
int maxlogn;

void init(){
    for(int i=1;i<=n;i++){
        dp[i][0]=a[i];
    }
    for(int j=1;j<=maxlogn;j++){
        for(int i=1;i+int(1<<j)-1<=n;i++){
            dp[i][j]=max(dp[i][j-1],dp[i+int(1<<(j-1))][j-1]);
        }
    }
}

int ask(int l,int r){
    int len=r-l+1;
    int p=log2(len/2)+1;
    return max(dp[l][p],dp[r-int(1<<p)+1][p]);
}

int main(){
    cin>>n>>askn;
    maxlogn=log2(n);
    for(int i=1;i<=n;i++){
        scanf("%d",&a[i]);
    }
    init();
    for(int i=1;i<=askn;i++){
        int t1,t2;
        scanf("%d%d",&t1,&t2);
        printf("%d
",ask(t1,t2));
    }
    return 0;
}

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