计蒜客 奇怪的报数游戏 （树状数组+二分）

 

 解析很不错的博客https://blog.csdn.net/m0_38033475/article/details/80372331

二分很好的博客https://blog.csdn.net/csdn_blog_lcl/article/details/78186710

ac代码：

#include<bits/stdc++.h>

using namespace std;

const int maxn=5e5+10;

int C[maxn];
bool flag[maxn];
int ans[maxn];
int a[maxn];
int n;

inline int lowbit(int x){
    return x&-x;
}

inline void change(int x){
    for(;x<=n;x+=lowbit(x)){
        C[x]++;
    }
}

inline int getsum(int x){
    int res=0;
    while(x){
        res+=C[x];
        x-=lowbit(x);
    }
    return res;
}

int main(){
    scanf("%d",&n);
    for(int i=1;i<n;i++){
        scanf("%d",a+i);
    }
    for(int i=n-1;i;i--){
        int l=1,r=n+1,mid;
        while(l<r){
            mid=l+r>>1;
            if(mid>a[i]+1+getsum(mid-1)){
                r=mid;
            }else if(mid<a[i]+1+getsum(mid-1)){
                l=mid+1;
            }else{
                while(mid<=n&&mid==a[i]+getsum(mid-1)+1){
                    mid++;
                }mid--;
                break;
            }
        }
        change(mid);
        ans[i]=mid;
        flag[mid]=true;
    }
    for(int i=1;i<=n;i++){
        if(!flag[i]){
            ans[0]=i;
            break;
        }
    }
    for(int i=0;i<n;i++){
        printf("%d\n",ans[i]);
    }
}