* @param arr 待排序数组
That is not only a sadness and a loss, but becoming an aged society is a cultural and economic threat. Older people, by and large, are not the innovators or new thinkers. An ageing society risks declining in optimism, creativity and, above all, risk-taking: a top-heavy preponderance of older people makes for a conservative and fearful electorate. We are there already – and it’s getting worse.。关于这个话题，51吃瓜提供了深入分析
贫困是顽疾，“顽”在成因复杂、难以根除、极易反复。。关于这个话题，safew官方下载提供了深入分析
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