進数変換
(library/number/base_convert.hpp)

• View this file on GitHub
• Last update: 2026-01-08 10:19:27+09:00
• Include: #include "library/number/base_convert.hpp"

進数変換

できること

• to進数に変換する
• 結果が42の場合、4, 2と配列で返す

計算量

$O(log_{\vert to \vert} x)$

使い方

vector<int> cvt = base_convert(x, 10);

Verified with

• 進数変換のテスト (tests/number.base_convert.test.cpp)

Code

#pragma once
vector<int> base_convert(long long x, int to) {
    vector<int> ret;
    long long t = 1, k = abs(to);
    while (x) {
        ret.emplace_back((x * t) % k);
        if (ret.back() < 0) ret.back() += k;
        x -= ret.back() * t;
        x /= k;
        t *= to / k;
    }
    if (ret.empty()) ret.emplace_back(0);
    reverse(ret.begin(), ret.end());
    return ret;
}

#line 2 "library/number/base_convert.hpp"
vector<int> base_convert(long long x, int to) {
    vector<int> ret;
    long long t = 1, k = abs(to);
    while (x) {
        ret.emplace_back((x * t) % k);
        if (ret.back() < 0) ret.back() += k;
        x -= ret.back() * t;
        x /= k;
        t *= to / k;
    }
    if (ret.empty()) ret.emplace_back(0);
    reverse(ret.begin(), ret.end());
    return ret;
}

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