Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note:
The solution set must not contain duplicate triplets.
Example:
Given array nums = [-1, 0, 1, 2, -1, -4], A solution set is: [ [-1, 0, 1], [-1, -1, 2] ]
给定一个包含 n 个整数的数组
nums，判断 nums 中是否存在三个元素 a，b，c ，使得 a + b + c = 0 ？找出所有满足条件且不重复的三元组。
注意：答案中不可以包含重复的三元组。
例如, 给定数组 nums = [-1, 0, 1, 2, -1, -4]， 满足要求的三元组集合为： [ [-1, 0, 1], [-1, -1, 2] ]
116ms
1 class Solution {
2 func threeSum(_ nums: [Int]) -> [[Int]] {
3 guard nums.count > 2 else { return [] }
4 var solutions = [[Int]]();
5 let sorted = nums.sorted() { $0 < $1 }
6 let count = sorted.count
7 var i = 0
8
9 while (i < count - 2) {
10 if (i == 0 || (i > 0 && sorted[i] != sorted[i - 1])) {
11 var left = i + 1
12 var right = count - 1
13 let num = sorted[i]
14
15 while (left < right) {
16 let currentSum = sorted[left] + sorted[right] + num
17
18 if (currentSum == 0) {
19 solutions.append([sorted[left], sorted[right], num])
20
21 while (left < right && sorted[left] == sorted[left + 1]) {
22 left += 1
23 }
24
25 while (left < right && sorted[right] == sorted[right - 1]) {
26 right -= 1
27 }
28 left += 1
29 right -= 1
30 } else if (currentSum < 0) {
31 left += 1
32 } else {
33 right -= 1
34 }
35 }
36 }
37
38 i += 1
39 }
40
41 return solutions
42 }
43 }
120ms
1 class Solution {
2 func threeSum(_ nums: [Int]) -> [[Int]] {
3 guard nums.count > 2 else {
4 return []
5 }
6
7 var results = [[Int]]()
8 let sortedNums = nums.sorted()
9
10 for i in 0..<sortedNums.count-1 {
11 if i > 0 && sortedNums[i] == sortedNums[i-1] {
12 continue
13 }
14 let target = 0 - sortedNums[i]
15 var low = i + 1
16 var high = nums.count - 1
17
18 while low < high {
19 let sum = sortedNums[low] + sortedNums[high]
20 if sum == target {
21 let result = [sortedNums[i], sortedNums[low], sortedNums[high]]
22 results.append(result)
23
24 while (low < high && sortedNums[low] == sortedNums[low+1]) {
25 low += 1
26 }
27 while (low < high && sortedNums[high] == sortedNums[high-1]) {
28 high -= 1
29 }
30 low += 1
31 high -= 1
32 } else if sum < target {
33 low += 1
34 } else {
35 high -= 1
36 }
37 }
38 }
39
40 return results
41 }
42 }
124ms
1 class Solution {
2 func threeSum(_ nums: [Int]) -> [[Int]] {
3 if nums.count < 3 {
4 return []
5 }
6
7 var result = [[Int]]()
8 var snums = nums.sorted()
9
10 for i in 0...snums.count-2 {
11 if i > 0 && snums[i] == snums[i-1] {
12 continue
13 }
14
15 var l = i + 1
16 var r = snums.count - 1
17
18 while l < r {
19 let s = snums[i] + snums[l] + snums[r]
20
21 if s == 0 {
22 result.append([snums[i], snums[l], snums[r]])
23 l += 1
24 r -= 1
25
26 while l < r && snums[l] == snums[l-1] {
27 l += 1
28 }
29
30 while l < r && snums[r] == snums[r+1] {
31 r -= 1
32 }
33 } else if s < 0 {
34 l += 1
35 } else {
36 r -= 1
37 }
38 }
39 }
40
41 return result
42 }
43 }
136ms
1 class Solution {
2 func threeSum(_ nums: [Int]) -> [[Int]] {
3 var nums = nums.sorted()
4 var result = [[Int]]()
5
6 for i in 0..<nums.count {
7 if i == 0 || i > 0 && nums[i] != nums[i-1] {
8 var left = i + 1, right = nums.count - 1
9 var sum = 0 - nums[i]
10 print(sum)
11 while left < right {
12 if nums[left] + nums[right] == sum {
13 result.append([nums[left], nums[right], nums[i]])
14 while left < right && nums[left] == nums[left + 1]{
15 left += 1
16 }
17 while left < right && nums[right] == nums[right - 1]{
18 right -= 1
19 }
20 left += 1
21 right -= 1
22 } else if nums[left] + nums[right] < sum {
23 left += 1
24 } else {
25 right -= 1
26 }
27 }
28 }
29 }
30 return result
31 }
32 }
148ms
1 import Foundation
2 class Solution {
3 func threeSum(_ nums: [Int]) -> [[Int]] {
4
5 var n = nums
6 n.sort()
7
8 var aIndex1: Int = 0
9 var aIndexLow: Int = 0
10 var aIndexHi: Int = 0
11
12 var aResult = [[Int]]()
13
14 var aTargetSum: Int = 0
15
16 while aIndex1 < (n.count - 2) {
17
18 //The sandwich principle.
19 aIndexLow = aIndex1 + 1
20 aIndexHi = n.count - 1
21
22 while (aIndexLow < aIndexHi) && (n[aIndex1] + n[aIndexLow]) <= aTargetSum {
23
24 var aSum = n[aIndex1] + n[aIndexLow] + n[aIndexHi]
25 if aSum == aTargetSum {
26 var aArr = [n[aIndex1], n[aIndexLow], n[aIndexHi]]
27 aResult.append(aArr)
28
29 aIndexHi -= 1
30 //Prevent dupes on hi
31 while aIndexLow < aIndexHi && n[aIndexHi + 1] == n[aIndexHi] {
32 aIndexHi -= 1
33 }
34
35 //Prevent dupes on low
36 aIndexLow += 1
37 while aIndexLow < aIndexHi && n[aIndexLow - 1] == n[aIndexLow] {
38 aIndexLow += 1
39 }
40 } else if aSum > aTargetSum {
41 aIndexHi -= 1
42 } else {
43 aIndexLow += 1
44 }
45 }
46
47 //prevent dupes with first index.
48 aIndex1 += 1
49 while aIndex1 < n.count && n[aIndex1 - 1] == n[aIndex1] {
50 aIndex1 += 1
51 }
52 }
53
54 return aResult
55 }
56 }
164ms
1 class Solution {
2 func twoSum(_ array: [Int], ignoreIndex i: Int, result: inout [[Int]]) {
3
4 var l = i + 1
5
6 let a = array[i]
7
8 var r = array.count - 1
9
10 if i > 0 && a == array[i - 1] {
11 return
12 }
13
14 while l < r {
15
16 let b = array[l]
17
18 if a + b > 0 {
19 return
20 }
21
22 let c = array[r]
23
24 var sum = a + b + c
25
26 if sum == 0 {
27 let indexes = [a, b, c]
28
29 result.append(indexes)
30
31 l += 1
32
33 while l < r && array[l] == b {
34 l += 1
35 }
36
37 } else if sum < 0 {
38 l += 1
39
40 while l < r && array[l] == b {
41 l += 1
42 }
43 } else if sum > 0 {
44 r -= 1
45
46 while l < r && array[r] == c {
47 r -= 1
48 }
49 }
50 }
51
52 }
53
54 func threeSum(_ nums: [Int]) -> [[Int]] {
55
56 var result = [[Int]]()
57
58 if nums.count < 3 {
59 return result
60 }
61
62 let array = nums.sorted {
63 return $0 < $1
64 }
65
66 for i in 0..<array.count - 2 {
67 if array[i] > 0 {
68 break
69 }
70
71 twoSum(array, ignoreIndex: i, result: &result)
72 }
73
74 return result
75 }
76 }
原文地址：https://www.cnblogs.com/strengthen/p/9884470.html
时间： 2024-10-09 02:09:54