洛谷P3048 [USACO12FEB]牛的IDCow IDs

P3048 [USACO12FEB]牛的IDCow IDs

题目描述

Being a secret computer geek, Farmer John labels all of his cows with binary numbers. However, he is a bit superstitious, and only labels cows with binary numbers that have exactly K "1" bits (1 <= K <= 10). The leading bit of each label is always a "1" bit, of course. FJ assigns labels in increasing numeric order, starting from the smallest possible valid label -- a K-bit number consisting of all "1" bits. Unfortunately, he loses track of his labeling and needs your help: please determine the Nth label he should assign (1 <= N <= 10^7).

FJ给他的奶牛用二进制进行编号，每个编号恰好包含K 个"1" (1 <= K <= 10)，且必须是1开头。FJ按升序编号，第一个编号是由K个"1"组成。

请问第N(1 <= N <= 10^7)个编号是什么。

输入输出格式

输入格式：

Line 1: Two space-separated integers, N and K.

输出格式：

输入输出样例

输入样例#1：

7 3

输出样例#1：

10110

#include<cstdio>
using namespace std;
int n,k,j;
int a[13];
int main(){
scanf("%d%d",&n,&k);
for(int i=1;i<=k;i++)a[i]=i;
for(int i=2;i<=n;i++){
j=1;
while(1){
a[j]++;
if(a[j]!=a[j+1])break;
a[j]=j;
j++;
}
}
j=k;
for(int i=a[k];i>=1;i--){
if(a[j]==i)printf("1"),j--;
else printf("0");
}
return 0;
}

100分 模拟？