Update frog-position-after-t-seconds.cpp

Author: kamyu104

C++/frog-position-after-t-seconds.cpp

@@ -2,6 +2,40 @@
 // Space: O(n)
 
 class Solution {
+public:
+    double frogPosition(int n, vector<vector<int>>& edges, int t, int target) {
+        unordered_map<int, vector<int>> G;
+        G[1] = {};
+        for (const auto& edge : edges) {
+            G[edge[0]].emplace_back(edge[1]);
+            G[edge[1]].emplace_back(edge[0]);
+        }
+        int choices = dfs(G, target, t, 1, 0);
+        return choices ? 1.0 / choices : 0.0;
+    }
+
+private:
+    int dfs(const unordered_map<int, vector<int>>& G,
+               int target, int t, int node, int parent) {
+        if (!t || !(G.at(node).size() - int(parent != 0))) {
+            return (node == target);
+        }
+        int result = 0;
+        for (const auto& child : G.at(node)) {
+            if (child == parent) {
+                continue;
+            }
+            if (result = dfs(G, target, t - 1, child, node)) {
+                break;
+            }
+        }
+        return result * (G.at(node).size() - int(parent != 0));
+    }
+};
+
+// Time:  O(n)
+// Space: O(n)
+class Solution2 {
 public:
     double frogPosition(int n, vector<vector<int>>& edges, int t, int target) {
         unordered_map<int, vector<int>> G;
@@ -24,7 +58,9 @@ class Solution {
             if (child == parent) {
                 continue;
             }
-            result += dfs(G, target, t - 1, child, node);
+            if (result = dfs(G, target, t - 1, child, node)) {
+                break;
+            }
         }
         return result / (G.at(node).size() - int(parent != 0));
     }