算法入门经典P149（二叉树编号）

#include<cstdio>
#include<cstring>
const int maxd = 20;
int s[1<<maxd];
int main(){
    int D,I;
    while(scanf("%d%d",&D,&I)==2){
        memset(s,0,sizeof(s));
        int k,n = (1<<D)-1;
        for(int i=0;i<I;i++){
            k = 1;
            for(;;){
                s[k] = !s[k];
                k = s[k]?k*2:k*2+1;
                if(k>n)break;
            }
        }
        printf("%d\n",k/2);
    }
    return 0;
}