Word Search solution

Author: kim-young

word-search/kimyoung.js

@@ -0,0 +1,34 @@
+var exist = function (board, word) {
+    const rowLen = board.length, colLen = board[0].length;
+    let visited = new Set(); // keep track of visited coordinates
+
+    function dfs(row, col, idx) {
+        if (idx === word.length) return true; // if idx equals word.length, it means the word exists
+        if (row < 0 || col < 0 ||
+            row >= rowLen || col >= colLen ||
+            board[row][col] !== word[idx] ||
+            visited.has(`${row}|${col}`)) return false; // possible cases that would return false
+
+
+        // backtracking
+        visited.add(`${row}|${col}`); 
+        let result = dfs(row + 1, col, idx + 1) || // dfs on all 4 directions
+            dfs(row - 1, col, idx + 1) ||
+            dfs(row, col + 1, idx + 1) ||
+            dfs(row, col - 1, idx + 1);
+        visited.delete(`${row}|${col}`);
+
+        return result;
+    }
+
+    for (let row = 0; row < rowLen; row++) {
+        for (let col = 0; col < colLen; col++) {
+            if(dfs(row, col, 0)) return true; // dfs for all coordinates
+        }
+    }
+
+    return false;
+};
+
+// time - O(m * n * 4^w) traverse through the matrix (m * n) and run dfs on each of the possible paths (4^w) 4 being 4 directions 
+// space - O(m * n  + w)