Codeforces 652D (one-dimensional tree array)

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There are n sticks, and the range of each stick is$[l_i,r_i]$, There are no two$r_i$I figured it out, asking how many sticks each stick completely covers.
The i-th stick covers the j-th stick, the necessary condition is$l_i \leq l_j$&&$r_j \leq r_i$.
Then sort according to l, with the same r of the same l in the front, and then sweep from the back to the front.

const int maxn = 2e5 + 10;
struct seg{
    int l, r, id;
    seg() {}
    void read() {
        scanf("%d%d", &l, &r);
    }
}s[maxn];
int h[maxn*2];
int n, m;
bool cmp(const seg& LEFT, const seg& RIGHT) {
    return LEFT.l < RIGHT.l || (LEFT.l == RIGHT.l && LEFT.r > RIGHT.r);
}
inline int Hash(int x) {
    return lower_bound(h + 1, h + 1 + m, x) - h;
}
struct BIT {
    int a[maxn*2];
    void add(int x, int v) {
        while(x < maxn*2) {
            a[x] += v;
            x += lowbit(x);
        }
    }
    int sum(int x) {
        int res = 0;
        while(x > 0) {
            res += a[x];
            x -= lowbit(x);
        }
        return res;
    }
}BIT;
int ans[maxn];
int main(int argc, const char * argv[])
{    
    // freopen("in.txt","r",stdin);
    // freopen("out.txt","w",stdout);
    // ios::sync_with_stdio(false);
    // cout.sync_with_stdio(false);
    // cin.sync_with_stdio(false);

    cin >> n;
    m = 0;
    Rep(i, 1, n) s[i].read(), s[i].id = i, h[++m] = s[i].l, h[++m] = s[i].r;
    sort(h + 1, h + 1 + m);
    m = unique(h + 1, h + 1 + m) - h - 1;
    sort(s + 1, s + 1 + n, cmp);
    for (int i = n;i >= 1;--i) {
        // cout << Hash(s[i].r) << endl;
        int o = BIT.sum(Hash(s[i].r));
        ans[s[i].id] = BIT.sum(Hash(s[i].r));
        BIT.add(Hash(s[i].r), 1);
    }
    Rep(i, 1, n) printf("%d\n", ans[i]);

    // showtime;
    return 0;
}