ST表求RMQ(区间最值问题)

点击这里

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
const int mxm=1e6+5;
int ans[mxm][21];
int query(int l,int r){
    
    
	int k=log2(r-l+1);
	return max(ans[l][k],ans[r-(1<<k)+1][k]);
}
int n,m;
int main(){
    
    
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;++i){
    
    
		scanf("%d",&ans[i][0]);
	}
	for(int j=1;j<=21;j++)
        for(int i=1;i+(1<<j)-1<=n;i++)
            ans[i][j]=max(ans[i][j-1],ans[i+(1<<(j-1))][j-1]);
	for(int i=1;i<=m;++i){
    
    
		int l,r;
		scanf("%d%d",&l,&r);
		printf("%d\n",query(l,r));
	}
	return 0;
}
//另一版:
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
const int mxm=1e6+5;
int ans[mxm][21];
int logn[mxm];
inline int read() {
    
    
  char c = getchar();
  int x = 0, f = 1;
  while (c < '0' || c > '9') {
    
    
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    
    
    x = x * 10 + c - '0';
    c = getchar();
  }
  return x * f;
}
void pre( ){
    
    
	logn[1]=0;
	logn[2]=1;
	for(int i=3;i<mxm;++i){
    
    
		logn[i]=logn[i/2]+1;
	}
}
int query(int l,int r){
    
    
	int k=logn[r-l+1];
	return max(ans[l][k],ans[r-(1<<k)+1][k]);
}
int n,m;
int main(){
    
    
	pre();
	n=read(),m=read();
	for(int i=1;i<=n;++i){
    
    
		ans[i][0]=read();
	}
	for(int j=1;j<=21;j++)
        for(int i=1;i+(1<<j)-1<=n;i++)
            ans[i][j]=max(ans[i][j-1],ans[i+(1<<(j-1))][j-1]);
	for(int i=1;i<=m;++i){
    
    
		int l,r;
		l=read(),r=read();
		printf("%d\n",query(l,r));
	}
	return 0;
}