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借光光YZC的福气(今天拿到Rank1),本来还可以更好的,前面吃M去了,ABC都很晚切,而且异常兴奋,结果WA了好多发
Describe:我们都知道,Home W的数学最厉害了。有一天,他又开始开动脑筋了,他想:“为什么数字总是要从1排列到n呢?”于是,Home W开始研究自己排列数字的方法。首先,他写下了1-n中所有的奇数(按照升序排列),然后他又写下了1-n中所有的偶数(按照升序排列),那么问题来了,在这样的排列方式下第k个数是什么呢?
Solution:第一发getLL 结果int n。。。推推公式,奇数有x=(n+1)/2个,x<=k→k*2-1,k-=x,剩下是偶数k*2
Code:
// <A.cpp> - Sun Oct 9 19:01:04 2016 // This file is made by YJinpeng,created by XuYike‘s black technology automatically. // Copyright (C) 2016 ChangJun High School, Inc. // I don‘t know what this program is. #include <iostream> #include <vector> #include <algorithm> #include <cstring> #include <cstdio> #include <cstdlib> #include <cmath> #define MOD 1000000007 #define INF 1e9 #define IN inline #define RG register using namespace std; typedef long long LL; typedef long double LB; const int MAXN=100010; const int MAXM=100010; inline int max(int &x,int &y) {return x>y?x:y;} inline int min(int &x,int &y) {return x<y?x:y;} inline LL gi() { register LL w=0,q=0;register char ch=getchar(); while((ch<‘0‘||ch>‘9‘)&&ch!=‘-‘)ch=getchar(); if(ch==‘-‘)q=1,ch=getchar(); while(ch>=‘0‘&&ch<=‘9‘)w=w*10+ch-‘0‘,ch=getchar(); return q?-w:w; } int main() { freopen("A.in","r",stdin); freopen("A.out","w",stdout); LL n=gi(),k=gi(); if(k<=(n+1)/2){ cout<<2*k-1;return 0; } k-=(n+1)/2;cout<<k*2; return 0; }
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原文地址:http://www.cnblogs.com/YJinpeng/p/5944174.html