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@@ -0,0 +1,72 @@
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+package main
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+
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+import (
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+ "fmt"
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+ "sort"
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+)
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+
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+func main() {
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+ var nums []int
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+ var target int
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+
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+ nums = []int{0, 0, 0, 0}
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+ target = 0
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+ fmt.Println(fourSum(nums, target))
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+
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+ return
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+
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+ nums = []int{1, 0, -1, 0, -2, 2}
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+ target = 0
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+ fmt.Println(fourSum(nums, target))
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+
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+ nums = []int{-3, -2, -1, 0, 0, 1, 2, 3}
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+ target = 0
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+ fmt.Println(fourSum(nums, target))
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+
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+ nums = []int{-3, 0, 0, 1, 2}
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+ target = 0
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+ fmt.Println(fourSum(nums, target))
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+}
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+
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+func fourSum(nums []int, target int) [][]int {
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+ sort.Ints(nums)
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+ var ret [][]int
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+ for i := 0; i < len(nums)-2; i++ {
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+ if i > 0 && nums[i] == nums[i-1] {
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+ continue
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+ }
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+ for j := i + 1; j < len(nums)-1; j++ {
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+ if j > i+1 && nums[j] == nums[j-1] {
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+ continue
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+ }
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+ var front, back = j + 1, len(nums) - 1
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+ var sum = 0
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+ for front < back {
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+ sum = nums[i] + nums[j] + nums[front] + nums[back] - target
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+ //fmt.Println(nums[i], nums[j], nums[front], nums[back], sum)
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+ if sum == 0 {
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+ ret = append(ret, []int{nums[i], nums[j], nums[front], nums[back]})
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+ for front < back {
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+ front++
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+ if nums[front] != nums[front-1] {
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+ break
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+ }
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+ }
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+ for front < back {
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+ back--
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+ if nums[back] != nums[back+1] {
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+ break
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+ }
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+ }
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+ }
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+ if sum > 0 {
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+ back--
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+ }
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+ if sum < 0 {
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+ front++
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+ }
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+ }
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+ }
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+ }
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+ return ret
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+}
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