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intermediatelayer B4 · Two pointers5 tests

nums contains only the values 0, 1 and 2. Sort it in place so all the 0s come first, then the 1s, then the 2s.

  • Mutate the array; the return value is ignored
  • Do it in a single pass with O(1) extra space
  • Counting each value and rewriting is two passes — aim better

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