65 lines
1.3 KiB
Go
65 lines
1.3 KiB
Go
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import "sort"
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type customSort struct {
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nums []int
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indices []int
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}
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func (c customSort) Len() int {
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return len(c.nums)
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}
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func (c customSort) Swap(i, j int) {
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c.indices[i], c.indices[j] = c.indices[j], c.indices[i]
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}
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func (c customSort) Less(i, j int) bool {
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oi := c.indices[i]
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oj := c.indices[j]
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return c.nums[oi] < c.nums[oj]
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}
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func twoSum(nums []int, target int) []int {
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// Alternate solution: using two stops
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// Make a slice containing indices to the original array
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si := make([]int, len(nums))
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for i, _ := range nums {
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si[i] = i
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}
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// Sort the slice of indices in ascending order. This hackery
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// is needed because that's how Go's custom sorting is implemented
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sort.Sort(customSort{
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nums: nums,
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indices: si,
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})
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lc := 0
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rc := len(si) - 1
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for lc < rc {
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// Remember: si[lc] gives me the "index to original slice",
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// which I can then use to get the left stop's value. Similarly
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// get the right stop value.
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l := nums[si[lc]]
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r := nums[si[rc]]
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if l+r == target {
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return []int{si[lc], si[rc]}
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}
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// Remember: if this is less, then we need to "increase the value" of
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// l + r. Since we are traversing in the sorted array, this can only
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// mean one thing — we increase the left stop
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if l+r < target {
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lc++
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} else {
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rc--
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}
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}
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// If we reach here, basically we didn't find the target
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return []int{}
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}
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