Minimizing Maximizer UVA

动态规划的一道题目，不难，利用线段树来实现时间上的优化，具体实现见如下代码：

#include<iostream>#include<vector>#include<string>#include<set>#include<stack>#include<queue>#include<map>#include<algorithm>#include<cmath>#include<iomanip>#include<cstring>#include<sstream>#include<cstdio>#include<deque>using namespace std;int tree[500005*4];class Solve{public:int n, m;const int Inf = 0x3f3f3f3f;void build(int root,int left,int right){tree[root] = Inf;if (left == right) return;int mid = (left + right) / 2;build(2 * root, left, mid);build(2 * root + 1, mid + 1, right);}int query(int root,int L,int R,int left,int right){if (left >= L&&right <= R) return tree[root];int mid = (left + right) / 2;if (R <= mid) return query(2 * root, L, R, left, mid);else if (L > mid) return query(2 * root + 1, L, R, mid + 1, right);else return min(query(2 * root, L, R, left, mid), query(2 * root + 1, L, R, mid + 1, right));}void update(int pos,int value,int root,int left,int right){if (tree[root] > value) tree[root] = value;if (left == right) return;int mid = (left + right) / 2;if (pos <= mid) update(pos, value, 2 * root, left, mid);else update(pos, value, 2 * root + 1, mid+1, right);}void Deal(){cin >> n >> m;build(1,1,n);update(1, 0, 1, 1, n);for (int i = 0; i < m; i++){int a, b;cin >> a >> b;int x = query(1, a, b, 1, n);update(b, x + 1, 1, 1, n);}int res = query(1, n, n, 1, n);cout << res << endl;}};int main(){Solve a;int t;cin >> t;while (t--){a.Deal();if (t) cout << endl;}return 0;}