Bit Ceil
(misc/bit_ceil.hpp)

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• Last update: 2025-12-31 07:11:44+09:00
• Include: #include "misc/bit_ceil.hpp"

bit_ceil

T bit_ceil(T x)

$x \leq 2^m$ となる最小の $2^m$（$m$ は $0$ 以上の整数）を返します。

$x = 0$ のときは $1$ を返します。

制約

• $x \geq 0$

Verified with

• misc/test/bit_operation.test.cpp

Code

#pragma once

#include <cassert>

#if __cplusplus >= 202002L
#include <bit>
#endif

// bit_ceil
// (0, 1, 2, 3, 4) -> (1, 1, 2, 4, 4)
#if __cplusplus >= 202002L
using std::bit_ceil;
#else
unsigned int bit_ceil(unsigned int x) {
    unsigned int p = 1;
    while (p < x) p *= 2;
    return p;
}
unsigned long long int bit_ceil(unsigned long long int x) {
    unsigned long long int p = 1;
    while (p < x) p *= 2;
    return p;
}
#endif
int bit_ceil(int x) {
    assert(x >= 0);
    return bit_ceil((unsigned int)(x));
}
long long int bit_ceil(long long int x) {
    assert(x >= 0);
    return bit_ceil((unsigned long long int)(x));
}

#line 2 "misc/bit_ceil.hpp"

#include <cassert>

#if __cplusplus >= 202002L
#include <bit>
#endif

// bit_ceil
// (0, 1, 2, 3, 4) -> (1, 1, 2, 4, 4)
#if __cplusplus >= 202002L
using std::bit_ceil;
#else
unsigned int bit_ceil(unsigned int x) {
    unsigned int p = 1;
    while (p < x) p *= 2;
    return p;
}
unsigned long long int bit_ceil(unsigned long long int x) {
    unsigned long long int p = 1;
    while (p < x) p *= 2;
    return p;
}
#endif
int bit_ceil(int x) {
    assert(x >= 0);
    return bit_ceil((unsigned int)(x));
}
long long int bit_ceil(long long int x) {
    assert(x >= 0);
    return bit_ceil((unsigned long long int)(x));
}

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