Submission #1085433

#	Time	Username	Problem	Language	Result	Execution time	Memory
1085433		DucNguyen2007	K-th path (IZhO11_kthpath)	C++14	100 / 100	1 ms	464 KiB

kthpath

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
const int maxN=101;
const ll inf=2e18;
int n,m;
ll dp[maxN+1][maxN+1],k,comb[maxN+1][maxN+1];
char c[maxN+1][maxN+1];
vector<pii> v[26];
string s;
int main()
{
    //freopen("","r",stdin);
    //freopen("","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=m;j++)
        {
            cin>>c[i][j];
        }
    }
    cin>>k;
    for(int i=0;i<=60;i++)
    {
        comb[0][i]=1;
    }
    for(int i=1;i<=60;i++)
    {
        for(int j=i;j<=60;j++)
        {
            if(i==j)
            {
                comb[i][j]=1;
            }
            else comb[i][j]=comb[i-1][j-1]+comb[i][j-1];
        }
    }
    s+=c[1][1];
    dp[1][1]=1;
    for(int st=2;st<=n+m-1;st++)
    {
        ll res=0,cur=0;
        for(int ch=0;ch<26;ch++)
        {
            for(int i=1;i<=st;i++)
            {
                int j=st+1-i;
                if(c[i][j]-'a'==ch)
                {
                    dp[i][j]=dp[i-1][j]+dp[i][j-1];
                    res+=(dp[i][j]*comb[n-i][n-i+m-j]);
                }
                else dp[i][j]=0;
            }
            if(res>=k)
            {
                s+=(char)(ch+'a');
                k-=cur;
                break;
            }
            cur=res;
        }
    }
    cout<<s;
}

• Subtask 1: 100 / 100