Lua二分查找：有序数组的一次对半

-- 错误：有序表也线性逐个比，浪费排序的价值
for i, v in ipairs(rank) do
    if v == target then
        return i
    end
end

local function binSearch(a, target)
    local lo, hi = 1, #a
    while lo <= hi do
        local mid = math.floor((lo + hi) / 2)
        if a[mid] == target then
            return mid
        elseif a[mid] < target then
            lo = mid + 1
        else
            hi = mid - 1
        end
    end
    return 0
end
local rank = {12, 34, 56, 78, 90, 101}
local label = panel:getChildByName("myRank")
label:setString(tostring(binSearch(rank, 78)))