Merge pull request soapyigu#351 from soapyigu/String

Add a solution to Shortest Way to Form String

Author: soapyigu

String/ShortestWayFormString.swift

@@ -0,0 +1,30 @@
+/**
+ * Question Link: https://leetcode.com/problems/shortest-way-to-form-string/
+ * Primary idea: Iterate through source and consume same characters for the target
+ * Time Complexity: O(n), Space Complexity: O(1)
+ */
+
+class ShortestWayFormString {
+    func shortestWay(_ source: String, _ target: String) -> Int {
+        var res = 0, idx = 0
+        let s = Array(source), t = Array(target)
+        
+        while idx < t.count {
+            let pre = idx
+            
+            for i in 0..<s.count {
+                if idx < t.count && t[idx] == s[i] {
+                    idx += 1
+                }
+            }
+            
+            if pre == idx {
+                return -1
+            }
+            
+            res += 1
+        }
+        
+        return res
+    }
+}