Algorithms: Searching Tutorials and Code Examples - Page 9

Lower Bound in C++

A boundary search finds an insertion position in a sorted array, including arrays with repeated values.

cpp

int lower_bound(const std::vector<int>& a, int target) {
    alg_require(a.size() <= 1000000);
    int n = (int)a.size();
    alg_require(((n >= 0) && (n <= 1000000)));
    alg_require(((int)a.size() == n));
    int lo = 0;
    int hi = n;
    int mid = 0;
    while ((lo < hi)) {
        mid = alg_add(lo, (alg_sub(hi, lo) / 2));
        if ((a[mid] < target)) {
            lo = alg_add(mid, 1);

Nov 15, 2026 C++

Algorithms: Searching

Lower Bound in C#

A boundary search finds an insertion position in a sorted array, including arrays with repeated values.

csharp

    static int lower_bound(ReadOnlySpan<int> a, int target) {
        checked {
            int n = a.Length;
            alg_require(((n >= 0) && (n <= 1000000)));
            alg_require((a.Length == n));
            int lo = 0;
            int hi = n;
            int mid = 0;
            while ((lo < hi)) {
                mid = (lo + ((hi - lo) / 2));
                if ((a[mid] < target)) {
                    lo = (mid + 1);

Nov 15, 2026 csharp

Algorithms: Searching

Lower Bound in PHP

A boundary search finds an insertion position in a sorted array, including arrays with repeated values.

php

function lower_bound(array $a, int $target): int {
    alg_require(array_is_list($a));
    $n = count($a);
    alg_require((($n >= 0) && ($n <= 1000000)));
    alg_require((count($a) == $n));
    $lo = 0;
    $hi = $n;
    $mid = 0;
    while (($lo < $hi)) {
        $mid = alg_add($lo, intdiv(alg_sub($hi, $lo), 2));
        if (($a[$mid] < $target)) {
            $lo = alg_add($mid, 1);

Nov 15, 2026 PHP

Algorithms: Searching

Binary Search in Java

Binary search repeatedly halves a sorted search interval.

java

    static int binary_search(int[] a, int target) {
        java.util.Objects.requireNonNull(a, "a");
        int n = a.length;
        alg_require(((n >= 0) && (n <= 1000000)));
        alg_require((a.length == n));
        int lo = 0;
        int hi = Math.subtractExact(n, 1);
        int mid = 0;
        while ((lo <= hi)) {
            mid = Math.addExact(lo, (Math.subtractExact(hi, lo) / 2));
            if ((a[mid] == target)) {
                return mid;

Nov 15, 2026 Java

Algorithms: Searching

Binary Search in JavaScript

Binary search repeatedly halves a sorted search interval.

javascript

function binary_search(a, target) {
    alg_require(a instanceof Int32Array);
    alg_require(Number.isInteger(target) && target >= -2147483648 && target <= 2147483647);
    let n = a.length;
    alg_require(((n >= 0) && (n <= 1000000)));
    alg_require((a.length == n));
    let lo = 0;
    let hi = alg_sub(n, 1);
    let mid = 0;
    while ((lo <= hi)) {
        mid = alg_add(lo, Math.floor(alg_sub(hi, lo) / 2));
        if ((a[mid] == target)) {

Nov 15, 2026 javascript