模板st表

Posted 2021-01-10 dukelv

吐个槽，我现在线段树敲得贼熟练，但是树状数组和st表这么强大的东西竟然基本不会！！！啊啊啊，我太菜了！

代码：

#include<iostream>
#include<cstdio>
#include<cmath>
#include<ctime>
#include<queue>
#include<algorithm>
#include<cstring>
using namespace std;
#define duke(i,a,n) for(int i = a;i <= n;i++)
#define lv(i,a,n) for(int i = a;i >= n;i--)
#define clean(a) memset(a,0,sizeof(a))
const int INF = 1 << 30;
const int N = 300005;
typedef long long ll;
typedef double db;
template <class T>
void read(T &x)
{
    char c;
    bool op = 0;
    while(c = getchar(), c < ‘0‘ || c > ‘9‘)
        if(c == ‘-‘) op = 1;
    x = c - ‘0‘;
    while(c = getchar(), c >= ‘0‘ && c <= ‘9‘)
        x = x * 10 + c - ‘0‘;
    if(op) x = -x;
}
template <class T>
void write(T x)
{
    if(x < 0) putchar(‘-‘), x = -x;
    if(x >= 10) write(x / 10);
    putchar(‘0‘ + x % 10);
}
int st[1000005][23],a[1000005],n,m;
void build()
{
    duke(i,1,n)
    st[i][0] = a[i];
    duke(i,1,21)
    {
        for(int j = 1;j + (1 << i) - 1 <= n;j++)
        {
            st[j][i] = max(st[j][i - 1],st[j + (1 << (i - 1))][i - 1]);
        }
    }
}
void query(int l,int r)
{
    int y = log2(r - l + 1);
    int maxn = 0;
    maxn = max(st[l][y],st[r - (1 << y) + 1][y]);
    printf("%d
",maxn);
}
int main()
{
    read(n);read(m);
    duke(i,1,n)
        read(a[i]);
    build();
    while(m--)
    {
        int l,r;
        read(l);read(r);
        query(l,r);
    }
    return 0;
}