Submission #332337

#	Time	Username	Problem	Language	Result	Execution time	Memory
332337		arujbansal	Coins (IOI17_coins)	C++17	100 / 100	14 ms	1964 KiB

coins

#include "coins.h"

std::vector<int> coin_flips(std::vector<int> b, int c) {
    std::vector<int> flips(1);
    
    int xorSum = 0;

    for (int i = 0; i < 64; i++)
        xorSum ^= b[i] * i;

    // xorSum ^ x = c
    // => xorSum ^ c = x
    // flip xorSum ^ c

    flips[0] = xorSum ^ c;

    return flips;
}

int find_coin(std::vector<int> b) {
    int c = 0;

    for (int i = 0; i < 64; i++)
        c ^= b[i] * i;

    return c;
}

• Subtask 1: 10 / 10
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 15 / 15
• Subtask 5: 50 / 50