spiral matrix solution

Author: yhkee0404

spiral-matrix/yhkee0404.kt

@@ -0,0 +1,30 @@
+class Solution {
+    fun spiralOrder(matrix: Array<IntArray>): List<Int> {
+        val visited = List(matrix.size) {MutableList(matrix.first().size) {false}} // T(n) = S(n) = O(n)
+        val drcs = listOf(
+            listOf(0, 1,),
+            listOf(1, 0,),
+            listOf(0, -1,),
+            listOf(-1, 0,),
+        )
+        val ans = mutableListOf<Int>()
+        search(ans, matrix, visited, drcs, 0, 0, 0, false)
+        return ans
+    }
+}
+
+fun search(ans: MutableList<Int>, matrix: Array<IntArray>, visited: List<MutableList<Boolean>>, drcs: List<List<Int>>, r: Int, c: Int, dir: Int, turned: Boolean) {
+    val drc = drcs[dir]
+    if (r == -1 || r == matrix.size || c == -1 || c == matrix.first().size || visited[r][c]) {
+        if (turned) {
+            return
+        }
+        val nDir = (dir + 1) % drcs.size
+        val nDrc = drcs[nDir]
+        search(ans, matrix, visited, drcs, r - drc[0] + nDrc[0], c - drc[1] + nDrc[1], nDir, true)
+        return
+    }
+    visited[r][c] = true
+    ans.add(matrix[r][c])
+    search(ans, matrix, visited, drcs, r + drc[0], c + drc[1], dir, false)
+}