Hey. I have a very large array and I want to find the Nth largest value. Trivially I can sort the array and then take the Nth element but I’m only interested in one element so there’s probably a better way than sorting the entire array…
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Hey. I have a very large array and I want to find the Nth largest value. Trivially I can sort the array and then take the Nth element but I’m only interested in one element so there’s probably a better way than sorting the entire array…
Sorting would require O(nlogn) runtime at minimum – There are very efficient selection algorithms which can solve your problem in linear time.
Partition-based selection(sometimesQuick select), which is based on the idea of quicksort (recursive partitioning), is a good solution (see link for pseudocode + Another example).