查看“Binary search”的源代码

二分法。

一般 pattern：
<syntaxhighlight lang=python>
low = 0
high = n
while low <= high:
    mid = (low + high) // 2
    mid_calc = f(mid)
    if mid_calc == target:
        return g(mid)
    elif mid_calc < target:
        low = mid + 1
    else:
        high = mid - 1
return default_retval
</syntaxhighlight>

注意 <code>'''low <= high'''</code>, <code>'''low = mid + 1'''</code> 和 <code>'''high = mid - 1'''</code>。

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