Segment Tree - Min

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pi32 = pair<int, int>;

const int maxN = 1e5 + 5;
const int INF = 1e9 + 7;
const int MOD = 998244353;

int n;
int a[maxN];

void build(int id, int l, int r) {
    if (l == r) {
        t[id] = a[l];
        return;
    }

    int mid = (l + r) / 2;
    build(id*2, l, mid);
    build(id*2 + 1, mid + 1, r);
    t[id] = min(t[id*2], t[id*2 + 1]);
}

// Cập nhập: a[pos] = val
void update(int id, int l, int r, int pos, int val) {
    if (pos < l || r < pos) return;
    if (l == r) {
        t[id] = val;
        return;
    }

    int mid = (l + r) / 2;
    update(id*2, l, mid, pos, val);
    update(id*2 + 1, mid+1, r, pos, val);

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

// Truy vấn: tìm min đoạn [u, v]
int getMin(int id, int l, int r, int u, int v) {
    if (v < l || r < u) return INF;
    if (u <= l && r <= v) return t[id];

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

int main() {
#ifdef LOCAL
    freopen("in1.txt", "r", stdin);
#else
    freopen("Segment Tree - Min.inp", "r", stdin);
    freopen("Segment Tree - Min.out", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

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

    build(1, 1, n);

    return 0;
}