Submission #836730

#	Time	Username	Problem	Language	Result	Execution time	Memory
836730		Tigerpants	Paint By Numbers (IOI16_paint)	C++17	100 / 100	275 ms	85212 KiB

paint

#include "paint.h"
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <numeric>
#include <functional>
#include <algorithm>
#include <cstdlib>
#include <string>

using namespace std;

typedef long long int ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef pair<bool, bool> pbo;
typedef vector<pbo> vpbo;
typedef vector<bool> vb;

const ll MAXN = 200000;
const ll MAXK = 100;

#define rep(i, a, b) for (ll i = a; i < b; i++)
#define sz(a) (ll) a.size()
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define trav(i, a, t) for (t::iterator i = a.begin(); i != a.end(); i++)

ll n, k;
vll c;

bool fdp[MAXN + 1][MAXK + 1][2];
bool bdp[MAXN + 1][MAXK + 1][2];

vll white; // white[i] = #white in [0, i)
vll black; // . . .

bool inline no_white(ll l, ll r) { // check if interval [l, r] has no white
    return white[r + 1] == white[l]; // white[r + 1] == white[r] + P[r] = ... = P[r] + P[r - 1] + ... + P[l] + while[l]
}

bool inline no_black(ll l, ll r) { // check if interval [l, r] has no black
    return black[r + 1] == black[l];
}

std::string solve_puzzle(std::string s, std::vector<int> c_) {
    //cout << "solve_puzzle" << endl;

    n = sz(s);
    k = sz(c_);
    c.resize(k);
    rep(i, 0, k) c[i] = c_[i];

    //cout << "clear fdp bdp" << endl;
    rep(i, 0, MAXN + 1) {
        rep(j, 0, MAXK + 1) {
            fdp[i][j][0] = false;
            fdp[i][j][1] = false;
            bdp[i][j][0] = false;
            bdp[i][j][1] = false;
        }
    }

    //cout << "white & black" << endl;
    // prefix sum
    white.resize(n + 1);
    black.resize(n + 1);
    white[0] = 0; black[0] = 0;
    rep(i, 0, n) {
        white[i + 1] = white[i] + (s[i] == '_');
        black[i + 1] = black[i] + (s[i] == 'X');
    }

    //cout << "forward dp" << endl;
    fdp[0][0][1] = no_white(0, c[0] - 1);
    fdp[0][0][0] = no_black(0, 0);
    // do forward_dp
    rep(x, 1, n) {
        rep(i, 0, k) {
            if (x + c[i] <= n) {
                fdp[x][i][1] = fdp[x - 1][i][0] & no_white(x, x + c[i] - 1);
            }
        }
        // i == 0
        fdp[x][0][0] = fdp[x - 1][0][0] & no_black(x, x);

        rep(i, 1, k + 1) {
            if (x >= c[i - 1]) {
                fdp[x][i][0] = (fdp[x - 1][i][0] | fdp[x - c[i - 1]][i - 1][1]) & no_black(x, x);
            } else {
                fdp[x][i][0] = fdp[x - 1][i][0] & no_black(x, x);
            }
        }
        /* rep(i, 0, k) {
            fdp[x][i][1] = fdp[x - 1][i][0] & no_white(x, x + c[i] - 1);
            fdp[x][i][0] = (fdp[x - 1][i][0] | fdp[x - c[i - 1]][i - 1][1]) & no_black(x, x);
        } */
    }

    //cout << "backward dp" << endl;
    bdp[n - c[k - 1]][k - 1][1] = no_white(n - c[k - 1], n - 1);
    //bdp[n][k][0] = true;
    bdp[n - 1][k][0] = no_black(n - 1, n - 1);
    // do backward_dp
    for (ll x = n - 2; x >= 0; x--) {
        rep(i, 0, k) {
            if (x + c[i] <= n) {
                /* if ((x == 0) && (i == 0)) {
                    cout << "here: " << bdp[x + c[i]][i + 1][0] << " " << no_white(x, x + c[i] - 1) << endl;
                } */
                bdp[x][i][1] |= bdp[x + c[i]][i + 1][0] & no_white(x, x + c[i] - 1);
            }
        }
        rep(i, 0, k) {
            bdp[x][i][0] = (bdp[x + 1][i][0] | bdp[x + 1][i][1]) & no_black(x, x);
        }
        bdp[x][k][0] = bdp[x + 1][k][0] & no_black(x, x);
        /* rep(i, 0, k) {
            bdp[x][i][1] = bdp[x + c[i]][i + 1][0] & no_white(x, x + c[i] - 1);
            bdp[x][i][0] = (bdp[x + 1][i][0] | bdp[x + 1][i + 1][1]) & no_black(x, x);
        } */
    }

    //cout << "compile possibilities" << endl;
    vb can_be_white(n, false);
    vb can_be_black(n, false);
    vll black_sweep(n, 0);

    rep(x, 0, n) {
        rep(i, 0, k + 1) {
            if (fdp[x][i][0] & bdp[x][i][0]) {
                can_be_white[x] = true;
            }
            if (fdp[x][i][1] & bdp[x][i][1]) {
                black_sweep[x]++;
                black_sweep[x + c[i]]--;
            }
        }
    }

    //cout << "sweep:" << endl;
    ll sweep = 0;
    rep(x, 0, n) {
        sweep += black_sweep[x];
        can_be_black[x] = (sweep > 0);
        //cout << sweep << " ";
    }
    //cout << endl;

    //cout << "gen answer" << endl;
    string answ;
    rep(x, 0, n) {
        answ += can_be_white[x] ? (can_be_black[x] ? '?' : '_') : (can_be_black[x] ? 'X' : '.');
    }
    //cout << answ << endl;



    /* cout << "fdp" << endl;;
    cout << "white:" << endl;
    rep(i, 0, k + 1) {
        rep(x, 0, n) {
            cout << fdp[x][i][0] << " ";
        }
        cout << endl;
    }
    cout << "black:" << endl;
    rep(i, 0, k + 1) {
        rep(x, 0, n) {
            cout << fdp[x][i][1] << " ";
        }
        cout << endl;
    }

    cout << "bdp" << endl;;
    cout << "white:" << endl;
    rep(i, 0, k + 1) {
        rep(x, 0, n) {
            cout << bdp[x][i][0] << " ";
        }
        cout << endl;
    }
    cout << "black:" << endl;
    rep(i, 0, k + 1) {
        rep(x, 0, n) {
            cout << bdp[x][i][1] << " ";
        }
        cout << endl;
    }
     */

    return answ;
}

• Subtask 1: 7 / 7
• Subtask 2: 3 / 3
• Subtask 3: 22 / 22
• Subtask 4: 27 / 27
• Subtask 5: 21 / 21
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10