Update graph-valid-tree.cpp

kamyu104 · kamyu104 · commit ae9c396acdd8 · 2015-10-24T20:32:16.000+08:00
diff --git a/C++/graph-valid-tree.cpp b/C++/graph-valid-tree.cpp
@@ -10,6 +10,8 @@ class Solution {
     bool validTree(int n, vector<pair<int, int>>& edges) {
         if (edges.size() != n - 1) {
             return false;
+        } else if (n == 1) {
+            return true;
         }
 
         unordered_map<int, node> nodes;
@@ -23,17 +25,17 @@ class Solution {
 
         unordered_set<int> visited;
         queue<int> q;
-        q.emplace(0);
+        q.emplace(edges[0].first);
         while (!q.empty()) {
             int i = q.front();
             q.pop();
-            visited.insert(i);
+            visited.emplace(i);
             for (const auto& n : nodes[i].neighbors) {
                 if (n != nodes[i].parent) {
                     if (visited.find(n) != visited.end()) {
                         return false;
                     } else {
-                        visited.insert(n);
+                        visited.emplace(n);
                         nodes[n].parent = i;
                         q.emplace(n);
                     }
