【BZOJ3173】【Tjoi2013】最长上升子序列（树状数组）

传送门w：http://www.lydsy.com/JudgeOnline/problem.php?id=3173

QwQ这个题大多数做法都是Treap+Bit，然后窝看到了一个只用Bit的题解，感觉思路很巧妙啊：http://blog.csdn.net/d_william/article/details/9146757

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#define MaxN 111111
using namespace std;
int n;
struct Bit{
    int s[MaxN];
    int lowbit(int x) { return x&-x; } 
    
    void Reset() { memset(s, 0, sizeof(s)); }
    
    void add(int x, int c){
        int i = x;
        while (i <= n){
            s[i] += c;
            i += lowbit(i);
        }
    }    
    
    void updata(int x, int c){
        int i = x;
        while (i <= n){
            s[i] = max(s[i], c);
            i += lowbit(i);
        }
    }
    
    int query(int x){
        int ret = 0, i = x;
        while (i > 0){
            ret = max(ret, s[i]);
            i -= lowbit(i);
        }
        return ret;
    }
    
    int queryS(int x){
        int ret = 0, i = x;
        while (i > 0){
            ret += s[i];
            i -= lowbit(i);
        }
        return ret;
    }
    
}A, B;
int pos[MaxN], orz[MaxN], ans[MaxN];

int getpos(int x){
    int l = 0, r = n+1, mid;
    while (l + 1 < r){
        mid = (l+r) >> 1;
        int t = A.queryS(mid);
        if (t < x) l = mid;
        else r = mid;
    }
    return r;
}

int main(){
    scanf("%d", &n);
    A.Reset(); B.Reset();
    for (int i = 1; i <= n; i++) { scanf("%d", &pos[i]); pos[i]++; A.add(i, 1); }
    for (int i = n; i; i--){
        int p = getpos(pos[i]);
        orz[i] = p;
        A.add(p, -1);
    }
    for (int i = 1; i <= n; i++){
        int t = B.query(orz[i]-1)+1;
        ans[i] = max(ans[i-1], t);
        B.updata(orz[i], t);
    }
    for (int i = 1; i <= n; i++) printf("%d
", ans[i]);
    return 0;
}