写一段c++的线段树代码

下面是一个简单的线段树代码，用于查询区间最小值和区间和。

#include <stdio.h>
#include <stdlib.h>

#define MAXN 1000000

struct node {
    int l, r;
    int minv, sum;
} tree[MAXN << 2];

int a[MAXN];

void build(int p, int l, int r) {
    tree[p].l = l;
    tree[p].r = r;
    if (l == r) {
        tree[p].minv = a[l];
        tree[p].sum = a[l];
        return;
    }
    int m = (l + r) >> 1;
    build(p << 1, l, m);
    build(p << 1 | 1, m + 1, r);
    tree[p].minv = tree[p << 1].minv < tree[p << 1 | 1].minv ? tree[p << 1].minv : tree[p << 1 | 1].minv;
    tree[p].sum = tree[p << 1].sum + tree[p << 1 | 1].sum;
}

void update(int p, int x, int v) {
    if (tree[p].l == x && tree[p].r == x) {
        tree[p].minv = v;
        tree[p].sum = v;
        return;
    }
    int m = (tree[p].l + tree[p].r) >> 1;
    if (x <= m) update(p << 1, x, v);
    else update(p << 1 | 1, x, v);
    tree[p].minv = tree[p << 1].minv < tree[p << 1 | 1].minv ? tree[p << 1].minv : tree[p << 1 | 1].minv;
    tree[p].sum = tree[p << 1].sum + tree[p << 1 | 1].sum;
}

int query_min(int p, int l, int r) {
    if (tree[p].l == l && tree[p].r == r) {
        return tree[p].minv;
    }
    int m = (tree[p].l + tree[p].r) >> 1;
    if (r <= m) return query_min(p << 1, l, r);
    else if (l > m) return query_min(p << 1 | 1, l, r);
    else return query_min(p << 1, l, m) < query_min(p << 1 | 1, m + 1, r) ? query_min(p << 1, l, m) : query_min(p << 1 | 1, m + 1, r);
}

int query_sum(int p, int l, int r) {
    if (tree[p].l == l && tree[p].r == r) {
        return tree[p].sum;
    }
    int m = (tree[p].l + tree[p].r) >> 1;
    if (r <= m) return query_sum(p << 1, l, r);
    else if (l > m) return query_sum(p << 1 | 1, l, r);
    else return query_sum(p << 1, l, m) + query_sum(p << 1 | 1, m + 1, r);
}

int main() {
    int n, m;
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);
    }
    build(1, 1, n);
    while (m--) {
        int op, x, y;
        scanf("%d%d%d", &op, &x, &y);
        if (op == 1) {
            update(1, x, y);
        } else if (op == 2) {
            printf("%d\n", query_min(1, x, y));
        } else if (op == 3) {
            printf("%d\n", query_sum(1, x, y));
        }
    }
    return 0;
}