#117 · #2001 · Number of Pairs of Interchangeable Rectangles(可互换矩形的组数)

You are given n rectangles, each [width_i, height_i]. Two rectangles are interchangeable if their width-to-height ratios are equal. Count the number of pairs (i, j) with i < j that are interchangeable. Constraints: 1 <= n <= 10^5, 1 <= width_i, height_i <= 10^5.