solution448.go

package solution448

// ============================================================================
// 448. Find All Numbers Disappeared in an Array
// URL: https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/
// ============================================================================

/*

	$ go test -bench=. -benchmem
	goos: linux
	goarch: amd64
	cpu: 13th Gen Intel(R) Core(TM) i7-13700K
	Benchmark_find-24    	 7476871	       156.5 ns/op	      24 B/op	       2 allocs/op

*/

func findDisappearedNumbers(nums []int) []int {
	stack := make([]int, 0)
	freq := make(map[int]int)
	val := 0
	maxval := len(nums)
	for i := 0; i < maxval; i++ {
		val = nums[i]
		_, ok := freq[val]
		if !ok {
			freq[val] = 1
		} else {
			freq[val]++
		}
	}
	for i := 1; i <= maxval; i++ {
		_, ok := freq[i]
		if !ok {
			stack = append(stack, i)
		}
	}
	return stack
}