2013 长沙网络赛 B 题 Bizarre Routine

题解

http://blog.csdn.net/u010257508/article/details/11936129

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int maxn=1e4+9;
int mint[maxn],maxt[maxn],ans[maxn];
int n,t,a,b;
void dfs(int t,int s,int sum)
{
    if(t>=s)
    {
        if(t==s) ans[t]=t;
        return ;
    }
    sum-=s-t;
    int i;
    for(i=t;;i++)
    if(maxt[i-t]+maxt[s-i]>=sum&&mint[i-t]+mint[s-i]<=sum) break;
    int l=mint[i-t],r=maxt[i-t],mid;
    while(l<r)
    {
        mid=l+r>>1;
        if(mid+maxt[s-i]<sum) l=mid+1;
        else r=mid;
    }
    dfs(t,i-1,l);
    dfs(i+1,s,sum-l);
    ans[i]=i;
    int ss=(t*a+s*b)/(a+b);
    swap(ans[ss],ans[i]);
    if(i!=ss) swap(ans[i],ans[s]);
}
void solve()
{
    dfs(1,n,t);
    for(int i=1;i<n;i++)
    printf("%d ",ans[i]);
    cout<<ans[n]<<endl;
}
int main()
{
    for(int i=1;i<maxn;i++) maxt[i]=i*(i-1)>>1;
    mint[1]=0,mint[2]=1;
    for(int i=3;i<maxn;i++) mint[i]=mint[i>>1]+mint[i-1>>1]+i-1;
    while(scanf("%d %d %d %d",&n,&t,&a,&b)!=EOF)
    {
        if(t>maxt[n]||t<mint[n]) printf("NOWAY\n");
        else solve();
    }
    return 0;
}