3Sum Closest.

Author: recherst

Medium/15.3Sum.playground/Contents.swift

@@ -38,7 +38,7 @@ class Solution {
             if sortedNums[i] > 0 {
                 break
             }
-            // Remove duplicate elements.
+            // filter duplicate elements.
             if i > 0 && sortedNums[i] == sortedNums[i - 1] {
                 continue
             }
@@ -48,7 +48,7 @@ class Solution {
                 if sortedNums[i] + sortedNums[left] + sortedNums[right] == 0 {
                     res.append([sortedNums[i], sortedNums[left], sortedNums[right]])
 
-                    // Remove duplicate elements.
+                    // filter duplicate elements.
                     while left < right && sortedNums[right] == sortedNums[right - 1] {
                         right -= 1
                     }

Medium/16.3Sum Closest.playground/Contents.swift

@@ -0,0 +1,52 @@
+/**
+ Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target.
+
+ Return the sum of the three integers.
+
+ You may assume that each input would have exactly one solution.
+
+  
+
+ Example 1:
+ Input: nums = [-1,2,1,-4], target = 1
+ Output: 2
+ Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
+ 
+ Example 2:
+ Input: nums = [0,0,0], target = 1
+ Output: 0
+  
+
+ Constraints:
+ - 3 <= nums.length <= 1000
+ - -1000 <= nums[i] <= 1000
+ - -10^4 <= target <= 10^4
+ */
+class Solution {
+    func threeSumClosest(_ nums: [Int], _ target: Int) -> Int {
+        let sortedNums = nums.sorted(by: <)
+        var closestNum = sortedNums[0] + sortedNums[1] + sortedNums[2]
+        for i in 0..<sortedNums.count - 2 {
+            var left = i + 1
+            var right = sortedNums.count - 1
+            while left < right {
+                let sumThree = sortedNums[i] + sortedNums[left] + sortedNums[right]
+                if abs(sumThree - target) < abs(closestNum - target) {
+                    closestNum = sumThree
+                }
+                if sumThree > target {
+                    right -= 1
+                } else if sumThree < target {
+                    left += 1
+                } else {
+                    return target
+                }
+            }
+        }
+        return closestNum
+    }
+}
+
+let s = Solution()
+let r = s.threeSumClosest([0, 1, 2], 3)
+print(r)

Medium/16.3Sum Closest.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Medium/16.3Sum Closest.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -114,3 +114,4 @@
 7. [Container With Most Water](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/11.Container%20With%20Most%20Water.playground/Contents.swift)
 8. [Integer to Roman](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/12.Integer%20to%20Roman.playground/Contents.swift)
 9. [3Sum](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/15.3Sum.playground/Contents.swift)
+10. [3Sum Closest](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/16.3Sum%20Closest.playground/Contents.swift)