Merge pull request soapyigu#345 from soapyigu/Graph

Add a solution to Find All Possible Recipes from Given Supplies

Author: soapyigu

Graph/FindAllPossibleRecipesGivenSupplies.swift

@@ -0,0 +1,46 @@
+/**
+ * Question Link: https://leetcode.com/problems/find-all-possible-recipes-from-given-supplies/
+ * Primary idea: Topological sort, keep each recipe with ingredients for a inDegree number and 
+ *               to recipe list, use a queue to decrease inDegree and form the result
+ *
+ * Time Complexity: O(n ^ 2), Space Complexity: O(n + m), 
+ * n represents the length of recipes, m represents the length of supplies
+ */
+
+class FindAllPossibleRecipesGivenSupplies {
+    func findAllRecipes(_ recipes: [String], _ ingredients: [[String]], _ supplies: [String]) -> [String] {
+        var (inDegrees, toRecipes) = buildGraph(recipes, ingredients)
+        var res = [String](), queue = supplies
+        
+        while !queue.isEmpty {
+            let food = queue.removeFirst()
+            
+            for recipe in toRecipes[food] ?? [] {
+                inDegrees[recipe]! -= 1
+                
+                if inDegrees[recipe] == 0 {
+                    res.append(recipe)
+                    queue.append(recipe)
+                }
+            }
+        }
+        
+        return res
+    }
+    
+    private func buildGraph(_ recipes: [String], _ ingredients: [[String]]) -> ([String: Int], [String: [String]]) {
+        var inDegrees = [String: Int]()
+        var toRecipes = [String: [String]]()
+        
+        for i in 0..<recipes.count {
+            let (recipe, recipeIngredients) = (recipes[i], ingredients[i])
+            
+            for ingredient in recipeIngredients {
+                inDegrees[recipe, default: 0] += 1
+                toRecipes[ingredient, default: []].append(recipe)
+            }
+        }
+        
+        return (inDegrees, toRecipes)
+    }
+}