From Evernote:

uva 679

這題感覺像分治，一開始有點難分析

不過抓到一些特徵就很好分析了

[sourcecode language="cpp"]
//============================================================================
// Name : Dropping Balls.cpp
// Date : 2013 2013/2/2 上午10:56:35
// Author : GCA
//============================================================================
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
typedef long long ll;
typedef unsigned int uint;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
printf("%d ",dp[htx][hty]);}Pln();}
#define M 3000005
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define Is_debug true
#define debug(...) if(Is_debug)printf("DEBUG: "),printf(__VA_ARGS__)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
int tmp=min(x,y);
return min(tmp,z);
}
int max3(int x,int y,int z){
int tmp=max(x,y);
return max(tmp,z);
}
int dc[25][M];
int n;
int pw2[25];
int query[25][M];
void dcc(int depth,int i){
if(depth>=n)return;
dc[depth][i<<1]=1;
dc[depth][i<<1|1]=2;
}
void pow2(){
int ans=1;
for(int i=0;i<23;i++,ans*=2)pw2[i]=ans;
}
int main() {
ios_base::sync_with_stdio(0);
pow2();
Set(dc,0);
dc[0][1]=1;
query[0][1]=1;
for(int i=0;i<23;i++){
for(int j=pw2[i];j<pw2[i+1];j++){
dc[i+1][j<<1]=dc[i][j];
query[i+1][dc[i][j]]=j<<1;
query[i+1][dc[i][j]+pw2[i]]=j<<1|1;
dc[i+1][j<<1|1]=dc[i][j]+pw2[i];
// printf("|%d %d",dc[i+1][j<<1],dc[i+1][j<<1|1]);
}
// Pln();
}
int test;
scanf("%d",&test);
while(test--){
int n,q;
scanf("%d%d",&n,&q);
printf("%d\n",query[n-1][q]);
}

}

[/sourcecode]