Page Comparison

func fourSum(nums []int, target int) (results [][]int) {
    sort.Ints(nums)

    i := 0
    for i < len(nums) - 3 {
        j := len(nums) - 1
        for i + 2 < j {
            partResults := twoSum(nums[i+1:j], target-(nums[i]+nums[j]))
            for _, r := range partResults {
                results = append(results,
                    []int{nums[i], r[0], r[1], nums[j]},
                )
            }
            for v := nums[j]; j > i+2 && nums[j] == v; j-- {}
        } 
         for v := nums[i]; i < len(nums)-3 && nums[i] == v; i++ {}
    }

    return
}

func twoSum(nums []int, target int) (results [][]int) {
    i, j := 0, len(nums)-1
    for i < j {
        sum := nums[i] + nums[j]
        if sum == target {
            results = append(results, []int{nums[i], nums[j]})

            for v := nums[i]; i < len(nums) && nums[i] == v; i++ {}
            for v := nums[j]; j >= 0 && nums[j] == v; j-- {}
        } else if sum < target {
            for v := nums[i]; i < len(nums) && nums[i] == v; i++ {}
        } else {
            for v := nums[j]; j >= 0 && nums[j] == v; j-- {}
        }
    }
    return
}

func fourSum(nums []int, target int) (results [][]int) {
    sort.Ints(nums)

    i := 0
    for i < len(nums) - 3 {
        partResults := threeSum(nums[i+1:], target-nums[i])
        for _, r := range partResults {
            results = append(results,
                append([]int{nums[i]}, r...),
            )
        }
        
        for v := nums[i]; i < len(nums)-3 && nums[i] == v; i++ {}
    }

    return
}

func threeSum(nums []int, target int) (results [][]int) {
    sort.Ints(nums)

    k := 0
    for k < len(nums) {
        partResults := twoSum(nums[k+1:], target-nums[k])
        for _, r := range partResults {
            results = append(results,
                append([]int{nums[k]}, r...),
            )
        }

        for v := nums[k]; k < len(nums) && nums[k] == v; k++ {}
    }
    
    return
}

func twoSum(nums []int, target int) (results [][]int) {
    i, j := 0, len(nums)-1
    for i < j {
        sum := nums[i] + nums[j]
        if sum == target {
            results = append(results, []int{nums[i], nums[j]})

            for v := nums[i]; i < len(nums) && nums[i] == v; i++ {}
            for v := nums[j]; j >= 0 && nums[j] == v; j-- {}
        } else if sum < target {
            for v := nums[i]; i < len(nums) && nums[i] == v; i++ {}
        } else {
            for v := nums[j]; j >= 0 && nums[j] == v; j-- {}
        }
    }
    return 
}

// nums should be already sorted
func nSum(nums []int, target int) (results [][]int) {

}