Submission #58133

#	Time	Username	Problem	Language	Result	Execution time	Memory
58133		Benq	K-th path (IZhO11_kthpath)	C++14	100 / 100	3 ms	936 KiB

kthpath

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 100001;

int N,M;
ll K, comb[61][61];
char g[30][30];
vector<array<ll,3>> v; // x, y, #
string ret;

ll getPath(int a, int b) {
    return comb[N-1-a+M-1-b][M-1-b];
}

void advance() {
    /*cout << "OH " << K << "\n";
    for (auto a: v) cout << a[0] << ' ' << a[1] << ' ' << a[2] << "\n";
    cout << "----\n";*/
    
    map<pi,ll> m;
    for (auto a: v) {
        if (a[0]+1 < N) m[{a[0]+1,a[1]}] += a[2];
        if (a[1]+1 < M) m[{a[0],a[1]+1}] += a[2];
    }
    
    vector<array<ll,4>> V;
    for (auto a: m) V.pb({int(g[a.f.f][a.f.s]-'a'),a.f.f,a.f.s,a.s});
    sort(all(V));
    int ind = 0;
    F0R(i,26) {
        ll cur = 0;
        int IND = ind;
        while (ind < sz(V) && V[ind][0] == i) {
            // cout << "HAHA " << V[ind][3] << " " << getPath(V[ind][1],V[ind][2]) << "\n";
            cur += V[ind][3]*getPath(V[ind][1],V[ind][2]);
            ind ++;
        }
        /*cout << "BLAH " << cur << " | "; 
        if (ind < sz(V)) cout << ind << " " << V[ind][0];
        cout << "\n";*/
        if (cur < K) {
            K -= cur;
        } else {
            v.clear();
            ret += char('a'+i);
            FOR(i,IND,ind) v.pb({V[i][1],V[i][2],V[i][3]});
            break;
        }
    }
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    F0R(i,61) {
        comb[i][0] = 1;
        FOR(j,1,i+1) comb[i][j] = comb[i-1][j]+comb[i-1][j-1];
    }
    cin >> N >> M;
    F0R(i,N) F0R(j,M) cin >> g[i][j];
    cin >> K;
    ret += g[0][0];
    v.pb({0,0,1});
    F0R(i,N+M-2) advance();
    cout << ret;
}

/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

• Subtask 1: 100 / 100