Submission #162712

#	Time	Username	Problem	Language	Result	Execution time	Memory
162712		rama_pang	Shortcut (IOI16_shortcut)	C++14	71 / 100	2041 ms	2168 KiB

shortcut

#include "shortcut.h"
#include <bits/stdc++.h>

#define NO_DEBUG
#define debug(x) cerr << #x << " is " << x << "\n"

using namespace std;
using lint = long long;

const lint INF = 1e18;

int N, C;
vector<lint> X;
vector<lint> D;

bool is_valid(lint T) {
    bool valid = false;
    lint max_sum = +INF; // maximum of S1 + S2 that is valid
    lint min_sum = -INF; // minimum of S1 + S2 that is valid
    lint max_dif = +INF; // maximum of S1 - S2 that is valid
    lint min_dif = -INF; // minimum of S1 - S2 that is valid

    for (int j = 0; j < N; j++) {
        for (int i = 0; i < j; i++) {
            if (X[j] - X[i] + D[j] + D[i] > T) { // minimize X[i] - D[i]
                max_sum = min(max_sum, + T - (- X[i] - X[j] + D[i] + D[j] + C));
                min_sum = max(min_sum, - T + (+ X[i] + X[j] + D[i] + D[j] + C));
                max_dif = min(max_dif, + T - (- X[i] + X[j] + D[i] + D[j] + C));
                min_dif = max(min_dif, - T + (+ X[i] - X[j] + D[i] + D[j] + C));
            }
        }
    }

    for (int i = 0, ptl = 0, ptr = N - 1; i < N && !valid; i++) {
        while (ptl <  N && X[ptl] - X[i] <  min_dif) ptl++;
        while (ptr >= 0 && X[ptr] + X[i] >= min_sum) ptr--;
        int pos = max(ptl, ptr + 1);
        valid |= (pos < N && min_sum <= X[pos] + X[i] && X[pos] + X[i] <= max_sum 
                          && min_dif <= X[pos] - X[i] && X[pos] - X[i] <= max_dif);
    }

    #ifndef NO_DEBUG
        cerr << "====================== ";
        debug(T);
        debug(max_sum);
        debug(min_sum);
        debug(max_dif);
        debug(min_dif);
        cerr << "\n\n";
    #endif

    return valid;
}

lint find_shortcut(int n_, vector<int> l_, vector<int> d_, int c_) {
    N = n_, C = c_;
    X.resize(N), D.resize(N);
    for (int i = 0; i < l_.size(); i++)
        X[i + 1] = X[i] + l_[i];
    for (int i = 0; i < d_.size(); i++)
        D[i] = d_[i];
    
    lint res = 0;
    for (lint L = 0, R = INF, M = (L + R) / 2; L <= R; M = (L + R) / 2) {
        if (is_valid(M))
            R = M - 1, res = M;
        else
            L = M + 1;
    }

    return res;
}

Compilation message (stderr)

shortcut.cpp: In function 'lint find_shortcut(int, std::vector<int>, std::vector<int>, int)':
shortcut.cpp:58:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < l_.size(); i++)
                     ~~^~~~~~~~~~~
shortcut.cpp:60:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < d_.size(); i++)
                     ~~^~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 14 / 14
• Subtask 3: 8 / 8
• Subtask 4: 7 / 7
• Subtask 5: 33 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3