feat: WEEK 04 solution (word-search)

Author: tigermint

word-search/tigermint.kt

@@ -0,0 +1,53 @@
+class Solution {
+
+    private val dx = intArrayOf(-1, 1, 0, 0)
+    private val dy = intArrayOf(0, 0, -1, 1)
+
+    fun exist(board: Array<CharArray>, word: String): Boolean {
+        val rows = board.size
+        val cols = board[0].size
+        val visited = Array(rows) { BooleanArray(cols) }
+
+        val starts = mutableListOf<Pair<Int, Int>>()
+        for (i in 0 until rows) {
+            for (j in 0 until cols) {
+                if (board[i][j] == word[0]) starts.add(i to j)
+            }
+        }
+
+        if (word.length == 1) return starts.isNotEmpty()
+
+        var flag = false
+
+        fun dfs(start: Pair<Int, Int>, index: Int) {
+            if (flag) return
+            if (index == word.length - 1) {
+                flag = true
+                return
+            }
+
+            for (i in 0 until 4) {
+                val nx = start.first + dx[i]
+                val ny = start.second + dy[i]
+
+                if (nx < 0 || nx >= rows) continue
+                if (ny < 0 || ny >= cols) continue
+                if (visited[nx][ny]) continue
+                if (word[index + 1] != board[nx][ny]) continue
+
+                visited[nx][ny] = true
+                dfs(Pair(nx, ny), index + 1)
+                visited[nx][ny] = false
+            }
+        }
+
+        for (start in starts) {
+            visited[start.first][start.second] = true
+            dfs(start, 0)
+            visited[start.first][start.second] = false
+            if (flag) return true
+        }
+
+        return false
+    }
+}