773. Sliding Puzzle

Author: amitbansal7

sliding-puzzle.cpp

@@ -0,0 +1,39 @@
+// Runtime: 8 ms
+// Memory Usage: 10 MB
+class Solution {
+public:
+  int slidingPuzzle(vector<vector<int>>& board) {
+    string src = "";
+    for (auto a : board) {
+      for (auto b : a) {
+        src += to_string(b);
+      }
+    }
+    set<string> vis;
+    vis.insert(src);
+    queue<string> q;
+    q.push(src);
+    vector<vector<int> > swps = {{1, 3}, {0, 2, 4}, {1, 5}, {0, 4}, {3, 1, 5}, {2, 4}};
+    int depth = 0;
+    string target = "123450";
+    while (!q.empty()) {
+      int sz = q.size();
+      for (int i = 0; i < sz; i++) {
+        src = q.front();
+        q.pop();
+        if (src == target) return depth;
+        int zero = src.find('0');
+        for (int s : swps[zero]) {
+          swap(src[zero], src[s]);
+          if (vis.find(src) == vis.end()) {
+            vis.insert(src);
+            q.push(src);
+          }
+          swap(src[s], src[zero]);
+        }
+      }
+      depth++;
+    }
+    return -1;
+  }
+};