找出给定数组内有多少重复的数，并打印它们对应的位置。

local t = {1, 7, 2, 5, 4, 9, 9, 7, 2, 2, 2, 5, 5}

function seekNum(t)
    local dic_count = {}

    local dic_pos = {}

    for i=1,#t do
        if dic_count[tostring(t[i])] == nil then
            dic_count[tostring(t[i])] = 1
        else
            local index = table.indexOf(t, t[i])
            dic_count[tostring(t[i])] = dic_count[tostring(t[i])] + 1

            local index = table.indexOf(t, t[i])
            if index > 0 then
                if dic_pos[tostring(index)] == nil then
                    dic_pos[tostring(index)] = t[i]
                end
            end
            dic_pos[i] = t[i]
        end
    end

    local tb_number = {}
    for number,count in pairs(dic_count) do
        if tonumber(count) ~= 1 then
            print("数字[ " .. number .. " ] 出现 [ " .. count .. " ]次")
            tb_number[#tb_number + 1] = number
        end
    end
    print("========================================")

    local T = {}
    for _,number in pairs(tb_number) do
        local _t = {}
        for pos,_number in pairs(dic_pos) do
            if number == tostring(_number) then
                table.insert(_t, pos)
            end
        end
        T[tostring(number)] = _t
    end

    for k,v in pairs(T) do
        print("数字[ ".. k .. " ]位置在")
        print("-------------------------")
        if type(v) == "table" then
            for _, _v in pairs(v) do
                print(_v)
            end
        end
        print("-------------------------")
    end
end

function table.indexOf(array, value)
    if array then
        local i, max = 1, #array
        while i <= max do
            if array[i] == value then
                return i
            end
            i = i + 1
        end
    end
    return -1
end

seekNum(t)

原文地址：https://www.cnblogs.com/lxyang0928/p/11140011.html