描述：给定字符串 num（非负整数）和整数 k，移除 k 位数字，使剩余数字最小。以字符串形式返回（不含前导零）。
These aren't contrived scenarios invented by test authors in total vacuum. They're consequences of the spec's design and reflect real world bugs.
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* 1. 转换视角：将"追车"问题转为"到达时间"比较（后车时间≤前车 → 合并）；
These gene variants can affect men and women, increasing the risk of a range of cancers, including prostate, breast and ovarian cancer.
Higher in the sky, Uranus will be sitting in the constellation Taurus and won't set until around midnight, giving skywatchers with the right equipment a better chance of tracking it down.