题意:给出归并排序的规则,构造一个长度为n的序列,使得序列按归并排序递归k次变为有序
思路:先构造一个有序序列,然后倒着模拟归并排序的递归过程,每次递归将有序变为无序
AC代码:
#include "iostream" #include "iomanip" #include "string.h" #include "stack" #include "queue" #include "string" #include "vector" #include "set" #include "map" #include "algorithm" #include "stdio.h" #include "math.h" #pragma comment(linker, "/STACK:102400000,102400000") #define bug(x) cout<<x<<" "<<"UUUUU"<<endl; #define mem(a,x) memset(a,x,sizeof(a)) #define step(x) fixed<< setprecision(x)<< #define mp(x,y) make_pair(x,y) #define pb(x) push_back(x) #define ll long long #define endl (" ") #define ft first #define sd second #define lrt (rt<<1) #define rrt (rt<<1|1) using namespace std; const ll mod=1e9+7; const ll INF = 1e18+1LL; const int inf = 1e9+1e8; const double PI=acos(-1.0); const int N=1e5+100; int n,k,a[N],f[N]; void dfs(int l, int r){ if(k<=1 || r<=l+1) return; k-=2; int mid=l+r>>1; swap(a[mid-1],a[mid]); dfs(l, mid); dfs(mid, r); } int main(){ ios::sync_with_stdio(0),cin.tie(0),cout.tie(0); cin>>n>>k; if((k&1)==0 || k>=2*n){ cout<<-1; return 0; } int d=log2(n)+1; for(int i=1; i<=n; ++i) a[i]=i; dfs(1, n+1); for(int i=1; i<=n; ++i) cout<<a[i]<<" "; return 0; }