Submission #159381

#	Time	Username	Problem	Language	Result	Execution time	Memory
159381		rama_pang	Paint By Numbers (IOI16_paint)	C++14	90 / 100	767 ms	524292 KiB

paint

#include "paint.h"
#include <bits/stdc++.h>
using namespace std;

string S;
int N, K;
vector<int> C;
vector<int> pref_white, pref_black;
vector<int> ans; //0 = undetermined, 1 = white, 2 = black, 3 = can be both
vector<vector<vector<int>>> memo;

inline bool check_white(int le, int ri) { //get number of white spaces in le...ri
    if (ri >= N) return false;
    if (le > ri) return true;
    int res = pref_white[ri];
    if (le > 0) res -= pref_white[le - 1]; 
    return (res == 0);
}

inline bool check_black(int le, int ri) { //get number of black spaces in le...ri
    if (ri >= N) return false;
    if (le > ri) return true;
    int res = pref_black[ri];
    if (le > 0) res -= pref_black[le - 1]; 
    return (res == 0);
}


bool dp(int n, int k, int last_black) {
    if (k == K) {
        if (check_black(n, N - 1)) {
            for (int i = n; i < N; i++) ans[i] |= 1;
            return true;
        }
        return false;
    }

    if (n == N) return false;

    if (memo[n][k][last_black] != -1) return memo[n][k][last_black];
    //if S[n] != '.', already determined. go next
    //assume S[n] = 'X' and '_'. if noth possible, '?'. 4 possibilities

    bool res_ = false, resX = false;

    if (S[n] == '_') {
        ans[n] |= 1;
        return memo[n][k][last_black] = dp(n + 1, k, 0);
    } else if (S[n] == 'X') {
        if (!last_black && check_white(n, n + C[k] - 1)) {
            bool res = dp(n + C[k], k + 1, 1);
            if (res) for (int i = n; i < n + C[k]; i++) ans[i] |= 2;
            return memo[n][k][last_black] = res;
        } else {
            return memo[n][k][last_black] = false;
        }
    }

    res_ = dp(n + 1, k, 0);
    if (!last_black && check_white(n, n + C[k] - 1)) resX = dp(n + C[k], k + 1, 1);
    
    if (res_) ans[n] |= 1;
    if (resX) for (int i = n; i < n + C[k]; i++) ans[i] |= 2;

    return memo[n][k][last_black] = (res_ || resX);
}

string solve_puzzle(string s, vector<int> c) {
    S = s;
    N = s.size();
    K = c.size();
    C = c;
    pref_white.resize(N);
    pref_black.resize(N);
    ans.resize(N);
    memo.assign(N, vector<vector<int>>(K, vector<int>(2, -1)));

    for (int i = 0; i < N; i++) {
        pref_white[i] = (S[i] == '_')? 1 : 0;
        if (i > 0) pref_white[i] += pref_white[i - 1];

        pref_black[i] = (S[i] == 'X')? 1 : 0;
        if (i > 0) pref_black[i] += pref_black[i - 1];
        
        
        if (S[i] == '.') {
            ans[i] = 0;
        } else if (S[i] == '_') {
            ans[i] = 1;
        } else if (S[i] == 'X') {
            ans[i] = 2;
        }
    }

    dp(0, 0, 0);

    string res;
    for (int i = 0; i < N; i++) {
        if (ans[i] == 0) {
            res.push_back('E');
        } else if (ans[i] == 1) {
            res.push_back('_');
        } else if (ans[i] == 2) {
            res.push_back('X');
        } else {
            res.push_back('?');
        }
    }

    return res;
}

Compilation message (stderr)

paint.cpp: In function 'bool dp(int, int, int)':
paint.cpp:48:39: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
         return memo[n][k][last_black] = dp(n + 1, k, 0);
paint.cpp:53:43: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
             return memo[n][k][last_black] = res;
paint.cpp:55:43: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
             return memo[n][k][last_black] = false;
paint.cpp:65:35: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     return memo[n][k][last_black] = (res_ || resX);

• 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: 0 / 10