feat: add swift solution 2 implementation to lcp problem: No.07 (#3743)

Author: klever34

lcp/LCP 07. 传递信息/README.md

@@ -255,6 +255,30 @@ function numWays(n: number, relation: number[][], k: number): number {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func numWays(_ n: Int, _ relation: [[Int]], _ k: Int) -> Int {
+        var f = Array(repeating: 0, count: n)
+        f[0] = 1
+        var steps = k
+        
+        while steps > 0 {
+            var g = Array(repeating: 0, count: n)
+            for r in relation {
+                let a = r[0], b = r[1]
+                g[b] += f[a]
+            }
+            f = g
+            steps -= 1
+        }
+        
+        return f[n - 1]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcp/LCP 07. 传递信息/Solution2.swift

@@ -0,0 +1,19 @@
+class Solution {
+    func numWays(_ n: Int, _ relation: [[Int]], _ k: Int) -> Int {
+        var f = Array(repeating: 0, count: n)
+        f[0] = 1
+        var steps = k
+        
+        while steps > 0 {
+            var g = Array(repeating: 0, count: n)
+            for r in relation {
+                let a = r[0], b = r[1]
+                g[b] += f[a]
+            }
+            f = g
+            steps -= 1
+        }
+        
+        return f[n - 1]
+    }
+}