线段树染色50pts求调

rt,WA#12345,hackAC,Code:

# include <bits/stdc++.h>

# define ffor(i,name) \
    for (auto i = name.begin (); i != name.end (); ++ i)

using namespace std;

typedef long long ll;

typedef pair <int, int> pii;

int n, m, a[1005], b[1005], sum;

bitset <40000005> tr, lazy;

void pushdown (int& x, int& l, int& r) {

    if (lazy[x]) {

        lazy[l] = lazy[r] = 1;

        tr[l] = tr[r] = 1;

        lazy[x] = 0;

    }

    return ;

}

void upd (int x, int l, int r, int L, int R) {

    if (l == L && r == R) {

        tr[x] = lazy[x] = 1;

        return ;

    }

    int mid = l + r >> 1, left = x << 1, right = left | 1;

    pushdown (x, left, right);

    if (R <= mid)
        upd (left, l, mid, L, R);
    else if (L > mid)
        upd (right, mid + 1, r, L, R);
    else
        upd (left, l, mid, L, mid), upd (right, mid + 1, r, mid + 1, R);

    return ;

}

bool find (int x, int l, int r, int L, int R) {

    if (l == L && r == R)
        return tr[x];

    int mid = l + r >> 1, left = x << 1, right = left | 1;

    pushdown (x, left, right);

    if (R <= mid)
        return find (left, l, mid, L, R);

    if (L > mid)
        return find (right, mid + 1, r, L, R);

    return find (left, l, mid, L, mid) && find (right, mid + 1, r, mid + 1, R);

}

int main () {

    ios::sync_with_stdio (0);

    cin.tie (0);

    cout.tie (0);

    cin >> n >> m;

    for (int i = 0; i < m; ++ i)
        cin >> a[i] >> b[i];

    while (m --)
        sum += ! find (1, 1, n, a[m], b[m]), upd (1, 1, n, a[m], b[m]);

    cout << sum;

    return 0;

}