[USACO03Open] Lost Cows（二分加树状数组）

#include<bits/stdc++.h>
using namespace std;
#define x first
#define y second
typedef pair<int,int> PII;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
typedef vector<string> VS;
typedef vector<int> VI;
typedef vector<vector<int>> VVI;
const int N = 1e4;
int a[N],b[N];
int n;
template <class T>
struct BIT
{
	T c[N];
	int sz;
	void init(int s)
	{
		sz = s;
		for(int i=1;i<=sz;++i) c[i] = 0;
	}
	T lowbit(int x)
	{
		return x&-x;
	}
	T sum(int x) 
	{
		assert(x <= sz);
		T res=0;
		while(x) res+=c[x],x-=lowbit(x);
		return res;
	}
	T query(int L, int R)
    {
        return sum(R) - sum(L-1);
    }
	void update(int x,int y) 
	{
		assert(x != 0);
		while(x<=sz) c[x]+=y,x+=lowbit(x);
	}
};
BIT<int> A;
void solve()
{
    cin>>n;
	A.init(n);
	for(int i=2;i<=n;++i) cin>>a[i];
	b[n] = a[n]+1;
	A.update(b[n],1);
	for(int i=n-1;i;--i)
	{
		int L = 0, R = n+1;
		while(L+1<R)
		{
			int M = (L+R)/2;
			//M-1为前面至多有多少小于M,-A.sum(M-1)是后面出现过的数
			if(M-1-A.sum(M-1)<=a[i]) L = M;
			else R = M;
		}
		b[i] = L;
		A.update(b[i],1);
	}
	for(int i=1;i<=n;++i) cout<<b[i]<<'\n';
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int T = 1;
	//cin>>T;
	while(T--)
	{
		solve();
	}
}