Submission #922677

#	Time	Username	Problem	Language	Result	Execution time	Memory
922677		thunopro	K-th path (IZhO11_kthpath)	C++14	100 / 100	2 ms	600 KiB

kthpath

#include<bits/stdc++.h>
using namespace std ; 
#define maxn 79 
#define ll long long 
#define fi first 
#define se second 
#define pb push_back 
#define left id<<1
#define right id<<1|1 
#define re exit(0); 

const int mod = 1e9+7; 
const int INF = 1e9; 

typedef vector<int> vi; 
typedef pair<int,int> pii;
typedef vector<pii> vii;  
typedef vector<ll> vl;

void add ( int &a , int b ) 
{
	a += b ; 
	if ( a > mod ) a -= mod ; 
	if ( a < 0 ) a += mod ; 
}

template <typename T> void chkmin ( T &a , T b ) { if ( a > b ) a = b ; }
template <typename T> void chkmax ( T &a , T b ) { if ( a < b ) a = b ; }

int _pow ( int a , int n ) 
{
	if ( n == 0 ) return 1 ;
	int res = _pow (a,n/2) ; 
	if ( n % 2 ) return 1ll*res*res%mod*a%mod ; 
	else return 1ll*res*res%mod ; 
}

void rf () 
{
	freopen ("bai1.inp","r",stdin) ;
}

int n , m ; 
ll k ; 
int ans [maxn] ; 
int a [maxn][maxn] ; 

ll dp [maxn][maxn] ; 

ll num_way ( int x , int y ) 
{
	if ( ans [x+y-1] != -1 && ans [x+y-1] != a [x][y] ) return 0 ; 
	if ( x == n && y == m ) return 1 ; 
	ll &res = dp [x][y] ; 
	if ( res + 1 ) return res ; 
	res = 0 ; 
	if ( x+1 <= n ) res += num_way (x+1,y) ; 
	if ( y+1 <= m ) res += num_way (x,y+1) ; 
	return res ; 
} 

int main () 
{
	ios_base::sync_with_stdio(0); 
	cin.tie(0);cout.tie(0); 
//	rf () ; 
	cin >> n >> m ; 
	for ( int i = 1 ; i <= n ; i ++ ) for ( int j = 1 ; j <= m ; j ++ ) 
	{
		char c ; cin >> c ; 
		a [i][j] = c - 'a' ; 
	}

	cin >> k ; 
	
	memset ( ans , -1 , sizeof ans ) ; 
	
	ans [1] = a [1][1] ; 
	
	for ( int run = 2 ; run < n+m ; run ++ ) 
	{
		for ( int ch = 0 ; ch < 26 ; ch ++ ) 
		{
			ans [run] = ch ; 
			memset ( dp , -1 , sizeof dp ) ; 
			if ( num_way (1,1) >= k ) break ; 
			else k -= num_way (1,1) ; 
		}
	}
	
	for ( int run = 1 ; run < n+m ; run ++ ) cout << char ('a'+ans[run]) ; 
}

Compilation message (stderr)

kthpath.cpp: In function 'void rf()':
kthpath.cpp:40:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   40 |  freopen ("bai1.inp","r",stdin) ;
      |  ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 100 / 100