HDU 3607 세그먼트 트리 + DP

/*
ID: CUGB-wwj
PROG:
LANG: C++
*/
#include <iostream>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
#define INF 1111111111
#define MAXN 111111
#define MAXM 444444
#define PI acos(-1.0)
#define L(X) X<<1
#define R(X) X<<1|1
using namespace std;
struct node
{
    int left, right, mid;
    int mx;
}tree[4 * MAXN];
int dp[MAXN];
int h[MAXN], x[MAXN];
void make_tree(int s, int e, int C)
{
    tree[C].left = s;
    tree[C].right = e;
    tree[C].mid = (s + e) >> 1;
    tree[C].mx = 0;
    if(s == e) return;
    make_tree(s, tree[C].mid, L(C));
    make_tree(tree[C].mid + 1, e, R(C));
}
void up(int C)
{
    tree[C].mx = max(tree[L(C)].mx, tree[R(C)].mx);
}
void update(int p, int v, int C)
{
    if(tree[C].left == tree[C].right)
    {
        tree[C].mx = max(tree[C].mx, v);
        return;
    }
    if(tree[C].mid >= p) update(p, v, L(C));
    else update(p, v, R(C));
    up(C);
}
int query(int s, int e, int C)
{
    if(tree[C].left >= s && tree[C].right <= e) return tree[C].mx;
    int ret = 0;
    if(tree[C].mid >= s) ret = max(ret, query(s, e, L(C)));
    if(tree[C].mid < e)  ret = max(ret, query(s, e, R(C)));
    return ret;
}
int cnt;
int bin(int v)
{
    int low = 1;
    int high = cnt;
    while(low <= high)
    {
        int mid = (low + high) >> 1;
        if(x[mid] == v) return mid;
        if(x[mid] > v) high = mid - 1;
        else low = mid + 1;
    }
    return -1;
}
int main()
{
    int n;
    while(scanf("%d", &n) != EOF)
    {
        for(int i = 1; i <= n; i++)
        {
            scanf("%d%d", &h[i], &dp[i]);
            x[i] = h[i];
        }
        sort(x + 1, x + n + 1);
        cnt = unique(x + 1, x + n + 1) - x - 1;
        make_tree(1, cnt, 1);
        int ans = 0;
        for(int i = 1; i <= n; i++)
        {
            int pos = bin(h[i]);
            int val;
            if(pos == 1) val = 0;
            else val = query(1, pos - 1, 1);
            dp[i] += val;
            ans = max(dp[i], ans);
            update(pos, dp[i], 1);
        }
        printf("%d
", ans);
    }
    return 0;
}