线段树

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e6 + 10, INF = 0x3f3f3f3f, MOD = 1E9 + 7;
int n, m;
struct Node {
    int l, r, x, lazy;  // x represents the number of lights on.
} tr[N << 2];

void pushup(Node& u, Node& l, Node& r) {
    u.x = l.x + r.x;
}
void pushup(int u) {
    pushup(tr[u], tr[u << 1], tr[u << 1 | 1]);
}
void pushdown(int u) {
    if (tr[u].lazy) {
        tr[u << 1].x = tr[u << 1].r - tr[u << 1].l + 1 - tr[u << 1].x;
        tr[u << 1].lazy = !tr[u << 1].lazy;
        tr[u << 1 | 1].x = tr[u << 1 | 1].r - tr[u << 1 | 1].l + 1 - tr[u << 1 | 1].x;
        tr[u << 1 | 1].lazy = !tr[u << 1 | 1].lazy;
        tr[u].lazy = 0;
    }
}
void build(int u, int l, int r) {
    tr[u] = {l, r, 0, 0};
    if (l == r) return;
    int mid = l + r >> 1;
    build(u << 1, l, mid), build(u << 1 | 1, mid + 1, r);
    pushup(u);
}
void modify(int u, int l, int r) {
    if (l <= tr[u].l && r >= tr[u].r) {
        tr[u].x = tr[u].r - tr[u].l + 1 - tr[u].x;
        tr[u].lazy = !tr[u].lazy;
        return;
    }
    pushdown(u);
    int mid = tr[u].l + tr[u].r >> 1;
    if (l <= mid) modify(u << 1, l, r);
    if (r > mid) modify(u << 1 | 1, l, r);
    pushup(u);
}
Node query(int u, int l, int r) {
    if (l <= tr[u].l && r >= tr[u].r) return tr[u];
    pushdown(u);
    int mid = tr[u].l + tr[u].r >> 1;
    Node res, left = {0, 0, 0}, right = {0, 0, 0};
    if (l <= mid) left = query(u << 1, l, r);
    if (r > mid) right = query(u << 1 | 1, l, r);
    pushup(res, left, right);
    return res;
}
int main(int argc, char* argv[]) {
    scanf("%d%d", &n, &m), build(1, 1, n);
    int op, l, r;
    while (m--) {
        scanf("%d%d%d", &op, &l, &r);
        if (op == 0) modify(1, l, r);
        else printf("%d\n", query(1, l, r).x);
    }
    return 0;
}