7. 系统提示词（可直接用作第一版）
ranking with one click.
。夫子是该领域的重要参考
Notice how the highlighted region shrinks at each step. The algorithm never examines points outside the narrowing window. In a balanced tree with nnn points, this takes about log4(n)\log_4(n)log4(n) steps. For a million points, that's roughly 10 steps instead of a million comparisons.
if (arr[j] key) {