ATL_DEV's questions

我不确定我做错了什么，但是当我执行下面的代码时：

func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
    let length = nums.count-1;

    for index1 in 0...length {
        let difference = target - nums[index1];
        print(target, difference, nums[index1])
        if (nums[index1] < difference) {
            for index2 in index1+1...length {
                if (nums[index2] == difference) {
                    return [index1, index2];
                }
            }
        }
    } 

    return [];
}

let summer = twoSum([-1,-2,-3,-4,-5], -8)

我收到以下错误：

Swift/ClosedRange.swift:347：致命错误：范围需要 lowerBound <= upperBound

有趣的是，如果我将 if 语句的条件更改为 nums[index1] <= target，它就不会崩溃。