competitive-programming-library

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a binary search / 二分探索 (utils/binary_search.hpp)

Code

#pragma once
#include <cassert>
#include <cstdint>

/**
* @brief a binary search / 二分探索
* @param[in] p  a monotone predicate defined on $[l, r)$
* @return $\min \lbrace x \in [l, r) \mid p(x) \rbrace$, or r if it doesn't exist
*/
template <typename UnaryPredicate>
int64_t binsearch(int64_t l, int64_t r, UnaryPredicate p) {
assert (l <= r);
-- l;
while (r - l > 1) {
int64_t m = l + (r - l) / 2;
(p(m) ? r : l) = m;
}
return r;
}

/**
* @return $\max \lbrace x \in (l, r] \mid p(x) \rbrace$, or l if it doesn't exist
*/
template <typename UnaryPredicate>
int64_t binsearch_max(int64_t l, int64_t r, UnaryPredicate p) {
assert (l <= r);
++ r;
while (r - l > 1) {
int64_t m = l + (r - l) / 2;
(p(m) ? l : r) = m;
}
return l;
}



#line 2 "utils/binary_search.hpp"
#include <cassert>
#include <cstdint>

/**
* @brief a binary search / 二分探索
* @param[in] p  a monotone predicate defined on $[l, r)$
* @return $\min \lbrace x \in [l, r) \mid p(x) \rbrace$, or r if it doesn't exist
*/
template <typename UnaryPredicate>
int64_t binsearch(int64_t l, int64_t r, UnaryPredicate p) {
assert (l <= r);
-- l;
while (r - l > 1) {
int64_t m = l + (r - l) / 2;
(p(m) ? r : l) = m;
}
return r;
}

/**
* @return $\max \lbrace x \in (l, r] \mid p(x) \rbrace$, or l if it doesn't exist
*/
template <typename UnaryPredicate>
int64_t binsearch_max(int64_t l, int64_t r, UnaryPredicate p) {
assert (l <= r);
++ r;
while (r - l > 1) {
int64_t m = l + (r - l) / 2;
(p(m) ? l : r) = m;
}
return l;
}