【luogu1816】忠誠

題面

RMQ問題

題解

線段樹

#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 100010;

int a[maxn];
struct node{
    int l, r;
    int val;
}sgt[maxn<<2];
void build(int p, int l, int r){
    sgt[p].l = l, sgt[p].r = r;
    if(l == r){
        sgt[p].val = a[l];
    }else{
        int m = (l+r)/2;
        build(p*2,l,m);
        build(p*2+1,m+1,r);
        sgt[p].val = min(sgt[p*2].val,sgt[p*2+1].val);
    }
}
int query(int p, int l, int r){
    if(l <= sgt[p].l && sgt[p].r <= r)return sgt[p].val;
    int m = (sgt[p].l+sgt[p].r)/2, ans = 0xffffff;
    if(l <= m)ans = min(ans, query(p*2,l,r));
    if(r > m)ans = min(ans, query(p*2+1,l,r));
    return ans;
}

int main(){
    int n, m;
    cin>>n>>m;
    for(int i = 1; i <= n; i++)cin>>a[i];
    build(1,1,n);
    for(int i = 1; i <= m; i++){
        int x, y;  cin>>x>>y;
        cout<<query(1,x,y)<<" ";
    }
}