Count Misordered Coin Pairs
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Count Misordered Coin Pairs
You are given a single stack of coins, represented by an integer array coins from top to bottom. Each coin has an integer value written on it. A pair of coins is considered misordered if a coin closer to the top has a greater value than a coin below it. Formally, for two positions i and j, the pair is misordered if: i < j and coins[i] > coins[j] Return the total number of misordered coin pairs in the stack. Equal-valued coins are not considered misordered.
Examples
coins = [2,4,1,3,5]
3
Explanation: The misordered pairs are (2,1), (4,1), and (4,3).
Approach hint
Compare the problem with counting how far the stack is from sorted order.
Common mistake
Skipping assumptions, edge cases, or trade-offs can make an otherwise good answer feel incomplete.