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twosum.go
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/
twosum.go
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package twosum
// 時間複雜 O(n^2), 空間複雜 O(1)
func Twosum(nums []int, target int) []int {
for i, _ := range nums {
for j := i + 1; j < len(nums); j++ {
if target == nums[i]+nums[j] {
return []int{i, j}
}
}
}
return []int{0, 0}
}
func Twosum2(nums []int, target int) []int {
m := make(map[int]int)
for i, v := range nums {
if idx, ok := m[target-v]; ok {
return []int{idx, i}
}
m[v] = i
}
return []int{0, 0}
}
// 如果nums是有序 可以使用左右指針
// func Twosum3(nums []int, target int) []int {
// left, right := 0, len(nums)-1
// sort.Ints(nums)
// for left < right {
// sum := nums[left] + nums[right]
// if sum == target {
// return []int{left, right}
// } else if sum < target {
// left++
// } else if sum > target {
// right--
// }
// }
// return []int{0, 0}
// }