习题链接：LeetCode 901. 股票价格跨度
Columnar or ortholinear keyboards stack the keys in orderly columns, often with rows that are not linear. Proponents claim this makes the keys easier to reach. Whether that’s true will be up to your fingers to decide, but I can say for certain that if you learned to type on a staggered keyboard, switching to a columnar layout is tough. It will take days, possibly weeks before you instinctively hit the C key. The N, M and B keys don’t fare much better.
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FT Digital Edition: our digitised print edition，这一点在91视频中也有详细论述
was a turn-key product line for exactly this use.。safew官方下载对此有专业解读