hihocoder1079 离散化

思路：
线段树 + 离散化。

测试用例：

3 10

1 10

1 3

6 10

实现：

 #include <bits/stdc++.h>
 using namespace std;
 typedef pair<int, int> pii;
 const int N = ;
 int tree[N << ], lazy[N << ], a[N];

 void init()
 {
     memset(tree, , sizeof tree);
     memset(lazy, , sizeof lazy);
 }

 void pushdown(int num, int cl, int cr)
 {
     if (!lazy[num]) return;
     tree[num << ] = lazy[num] * cl;
     tree[num <<  | ] = lazy[num] * cr;
     lazy[num << ] = lazy[num];
     lazy[num <<  | ] = lazy[num];
     lazy[num] = ;
 }

 void update(int num, int l, int r, int x, int y, int p)
 {
     if (x <= l && y >= r) { tree[num] = (r - l + ) * p; lazy[num] = p; return; }
     int m = l + r >> ;
     pushdown(num, m - l + , r - m);
     if (x <= m) update(num << , l, m, x, y, p);
     if (y >= m + ) update(num <<  | , m + , r, x, y, p);
     tree[num] = tree[num << ] + tree[num <<  | ];
 }

 int query(int num, int l, int r, int x, int y)
 {
     if (x <= l && y >= r) return tree[num];
     int m = l + r >> ;
     pushdown(num, m - l + , r - m);
     int ans = ;
     if (x <= m) ans += query(num << , l, m, x, y);
     if (y >= m + ) ans += query(num <<  | , m + , r, x, y);
     return ans;
 }

 int main()
 {
     ios::sync_with_stdio(false);
     init();
     int n, l, x, y;
     cin >> n >> l;
     vector<pii> q;
     vector<int> v;
     for (int i = ; i < n; i++)
     {
         cin >> x >> y;
         q.push_back(pii(x, y));
         v.push_back(x); v.push_back(y);
     }
     sort(v.begin(), v.end());
     v.erase(unique(v.begin(), v.end()), v.end());
     map<int, int> mp;
     for (int i = ; i < v.size(); i++) mp[v[i]] =  * i + ;
     int ans = , m = v.size() * ;
     for (int i = n - ; i >= ; i--)
     {
         int x = mp[q[i].first], y = mp[q[i].second];
         if (query(, , m, x, y) < y - x + ) ans++;
         update(, , m, x, y, );
     }
     cout << ans << endl;
     return ;
 }