feat: add swift implementation to lcof2 problem: No.102 (doocs#3614)

Author: klever34

lcof2/剑指 Offer II 102. 加减的目标值/README.md

@@ -163,6 +163,35 @@ func findTargetSumWays(nums []int, target int) int {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func findTargetSumWays(_ nums: [Int], _ target: Int) -> Int {
+        if target < -1000 || target > 1000 {
+            return 0
+        }
+        
+        let n = nums.count
+        var dp = Array(repeating: Array(repeating: 0, count: 2001), count: n)
+        
+        dp[0][nums[0] + 1000] += 1
+        dp[0][-nums[0] + 1000] += 1
+        
+        for i in 1..<n {
+            for j in -1000...1000 {
+                if dp[i - 1][j + 1000] > 0 {
+                    dp[i][j + nums[i] + 1000] += dp[i - 1][j + 1000]
+                    dp[i][j - nums[i] + 1000] += dp[i - 1][j + 1000]
+                }
+            }
+        }
+        
+        return dp[n - 1][target + 1000]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 102. 加减的目标值/Solution.swift

@@ -0,0 +1,24 @@
+class Solution {
+    func findTargetSumWays(_ nums: [Int], _ target: Int) -> Int {
+        if target < -1000 || target > 1000 {
+            return 0
+        }
+        
+        let n = nums.count
+        var dp = Array(repeating: Array(repeating: 0, count: 2001), count: n)
+        
+        dp[0][nums[0] + 1000] += 1
+        dp[0][-nums[0] + 1000] += 1
+        
+        for i in 1..<n {
+            for j in -1000...1000 {
+                if dp[i - 1][j + 1000] > 0 {
+                    dp[i][j + nums[i] + 1000] += dp[i - 1][j + 1000]
+                    dp[i][j - nums[i] + 1000] += dp[i - 1][j + 1000]
+                }
+            }
+        }
+        
+        return dp[n - 1][target + 1000]
+    }
+}