index = min(len(input), index + 1)
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，这一点在heLLoword翻译官方下载中也有详细论述
Transforms don't execute until the consumer pulls. There's no eager evaluation, no hidden buffering. Data flows on-demand from source, through transforms, to the consumer. If you stop iterating, processing stops.
if (arr[j] arr[j + 1]) { // 升序：前面的大于后面的就交换