Solve word ladder

127/input.txt

+1
+hit cog
+6
+hot dot dog lot log cog

127/word_ladder.cpp

+#include <iostream>
+#include <vector>
+#include <queue>
+
+using namespace std;
+
+class Node {
+public:
+    std::vector<Node*> adj;
+    std::string value;
+    bool marked;
+    static int length;
+
+    Node(string str) : value(str), marked(false) {}
+    ~Node() { adj.clear(); }
+};
+
+int Node::length = 0;
+
+int ladderLength(string beginWord, string endWord, vector<string>& wordList) {
+    std::vector<Node*> left, right;
+    Node::length = beginWord.length();
+
+    Node* start = new Node(beginWord);
+    left.push_back(start);
+
+    for (string word : wordList) {
+        left.push_back(new Node(word));
+    }
+
+    for (Node* parent : left) {
+        for (Node* child : left) {
+            int diff = 0;
+            for (int i = 0; i < Node::length; i++) {
+                if (parent->value[i] != child->value[i]) {
+                    diff++;
+                }
+            }
+            if (diff == 1) {
+                parent->adj.push_back(child);
+            }
+        }
+    }
+
+    // run BFS to find the node
+    std::queue<Node*> bfs;
+
+    start->marked = true;
+    bfs.push(start);
+    bfs.push(nullptr);
+    int depth = 1;
+
+    while (!bfs.empty()) {
+        Node* current = bfs.front();
+        bfs.pop();
+        if (current == nullptr) {
+            depth++;
+            bfs.push(nullptr);
+            if (bfs.front() == nullptr) return 0;
+        } else if (current->value.compare(endWord) == 0) {
+            return depth;
+        } else {
+            for (Node* child : current->adj) {
+                if (child->marked == false) {
+                    bfs.push(child);
+                    child->marked = true;
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
+int main () {
+    int iter;
+    std::string start, end;
+
+    std::cin >> iter;
+
+    for (int i = 0; i < iter; i++) {
+        std::cin >> start >> end;
+        int size;
+        std::string elem;
+        std::vector<std::string> list;
+        std::cin >> size;
+        for (int j = 0; j < size; j++) {
+            std::cin >> elem;
+            list.push_back(elem);
+        }
+        std::cout << ladderLength(start, end, list) << std::endl;
+    }
+}