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Binary search

Binary search finds a value in a sorted array by examining the middle element. Each comparison can remove about half the remaining candidates.

Try each step

Section titled “Try each step”
INTERACTIVE / LIVE

Binary search stepper

Pick a target, step forward and watch the search range change.

Live demo
SORTED ARRAY

Find a value by repeatedly halving the search range.

Select Next step to begin.

Step 0

Implementation in C#

Section titled “Implementation in C#”
C# | BinarySearch.cs
static int BinarySearch(int[] sorted, int target)
{
    int left = 0;
    int right = sorted.Length - 1;


    while (left <= right)
    {
        int middle = left + (right - left) / 2;


        if (sorted[middle] == target)
            return middle;


        if (sorted[middle] < target)
            left = middle + 1;
        else
            right = middle - 1;
    }


    return -1;
}

The time complexity is O(log n) and this iterative implementation uses O(1) additional space.