⚠️ 用 `lo < hi` 会怎样

下面这段二分把循环条件写成了 lo < hi，在 [13, 15, 17, 23, 24] 里找 24。运行它：

def buggy(a, target):
    lo = 0
    hi = len(a) - 1
    while lo < hi:
        mid = (lo + hi) // 2
        if a[mid] == target:
            return mid
        if a[mid] < target:
            lo = mid + 1
        else:
            hi = mid - 1
    return -1

print(buggy([13, 15, 17, 23, 24], 24))