CF507C Guess Your Way Out!

文章目录

ResultResultResult
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DescriptionDescriptionDescription
SolutionSolutionSolution
CodeCodeCode

ResultResultResult

HyperlinkHyperlinkHyperlink

https://www.luogu.com.cn/problem/CF507C

DescriptionDescriptionDescription

一棵高度为hhh的完全二叉树，按照LRLRLRLRLR……LRLRLRLRLR……LRLRLRLRLR……的顺序遍历，若遍历过或无路可走则回溯

求第nnn个访问到的节点
数据范围：h≤50,n≤250h\leq 50,n\leq 2^{50}h≤50,n≤250

SolutionSolutionSolution

考虑目标节点是否在当前所属节点的子树内，否则直接跳过这棵子树（因为这棵子树必然被遍历完），然后加上对应的节点数，不然再进入递归

时间复杂度：O(h)O(h)O(h)

CodeCodeCode

#include<cctype>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
using namespace std;int h;LL n,ans;bool fx;
inline LL read()
{char c;LL d=1,f=0;while(c=getchar(),!isdigit(c)) if(c=='-') d=-1;f=(f<<3)+(f<<1)+c-48;while(c=getchar(),isdigit(c)) f=(f<<3)+(f<<1)+c-48;return d*f;
}
signed main()
{h=read();n=read()-1;while(h--){if(((n>>h)&1)^fx) ans+=1ll<<(h+1);else ans++,fx^=1;}printf("%lld\n",ans);
}