NKLINEUP (Segment Tree)

//Tìm GTLN, GTNN trong từng đoạn [u, v]
#include <bits/stdc++.h>
using namespace std;

const int INF = 1e9 + 7;
const int N = 1e5 + 5;

int n, p, a[N];
long long stMax[4 * N], stMin[4 * N];

void buildMax(int id, int l, int r) {
    if (l == r) stMax[id] = a[l];
    else {
        int mid = (l + r) / 2;
        buildMax(id*2, l, mid);
        buildMax(id*2 + 1, mid + 1, r);

        stMax[id] = max(stMax[id*2], stMax[id*2 + 1]);
    }
}

void buildMin(int id, int l, int r) {
    if (l == r) stMin[id] = a[l];
    else {
        int mid = (l + r) / 2;
        buildMin(id*2, l, mid);
        buildMin(id*2 + 1, mid + 1, r);

        stMin[id] = min(stMin[id*2], stMin[id*2 + 1]);
    }
}

int getMax(int u, int v, int id, int l, int r) {
    if (v < l || r < u) return -INF;
    if (u <= l && r <= v) return stMax[id];

    int mid = (l + r) / 2;
    return max(getMax(u, v, id*2, l, mid), getMax(u, v, id*2 + 1, mid + 1, r));
}

int getMin(int u, int v, int id, int l, int r) {
    if (v < l || r < u) return INF;
    if (u <= l && r <= v) return stMin[id];

    int mid = (l + r) / 2;
    return min(getMin(u, v, id*2, l, mid), getMin(u, v, id*2 + 1, mid + 1, r));
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    cin >> n >> p;

    for (int i = 1; i <= n; ++i)
        cin >> a[i];

    buildMax(1, 1, n);
    buildMin(1, 1, n);

    while (p--){
       int u, v; cin >> u >> v;
       cout << getMax(u, v, 1, 1, n) - getMin(u, v, 1, 1, n) << '\n';
    }

    return 0;
}