初期Seedを計算

CalcInitialSeed.cpp

#include <iostream>
#include <iomanip>

using namespace std;

// 次の乱数を取得
uint32_t next(uint32_t s) {
    return 0x41C64E6D * s + 0x00006073;
}

// 前の乱数を取得
// 注:
// S[n+1] = (0x41C64E6D * S[n] + 0x6073) % 0x100000000
// に対して
// S[n-1] = (0xEEB9EB65 * S[n] + 0x0A3561A1) % 0x100000000
// が成り立つことを利用
uint32_t prev(uint32_t s) {
    return 0xEEB9EB65 * s + 0x0A3561A1;
}

// 実乱数を取得
uint16_t r(uint32_t s) {
    return (uint16_t) (s >> 16);
}

// 800F~3000Fで実現可能な初期Seedであれば真
bool is_feasible_initial_seed(uint32_t s_0) {
    int first_frame = 800;
    int last_frame = 10000; // 約3分

    // initial seed: 0xABCDEFGH
    int min_AB = 1 * 1 + 0 + 10;
    int max_AB = 12 * 31 + 59 + 59;
    int min_CD = 0;
    int max_CD = 23;
    int min_EFGH = first_frame;
    int max_EFGH = last_frame + 2099 - 2000;

    int AB = s_0 >> 24;
    int CD = (s_0 >> 16) % 0x100;
    int EFGH = s_0 % 0x10000;

    // 実現不可能な初期Seedを除外
    if (
            AB >= min_AB && AB <= max_AB
            && CD >= min_CD && CD <= max_CD
                               && EFGH >= min_EFGH && EFGH <= max_EFGH
            ) {
        return true;
    }
    return false;
}

void print_initial_seed_info(uint32_t s_n, int min_consumption) {
    uint32_t s = s_n;
    int n = 0;

    // 最小消費数分だけ先に消費
    for (int i = 0; i < min_consumption; i++) {
        s = prev(s);
        n++;
    }

    // 初期Seed候補の検索
    while(true) {
        s = prev(s);
        n++;

        // 実現可能な初期Seedがあれば情報を出力
        if (is_feasible_initial_seed(s)) {
            cout << setw(5) << dec << noshowbase << n;
            cout << setw(12) << hex << uppercase << showbase << s_n;
            cout << setw(12) << hex << uppercase << showbase << s << endl;
            break;
        }
    }
}

int main(void) {
    cout << setw(5) << "n";
    cout << setw(12) << "S[n]";
    cout << setw(12) << "S[0]" << endl;

    int min_consumption = 3;  // 徘徊ポケモンによる消費数分だけスキップ

    print_initial_seed_info(0x97024D60, min_consumption);
    print_initial_seed_info(0x015A9302, min_consumption);
    print_initial_seed_info(0xD62B4730, min_consumption);

    return 0;
}