Merge pull request #192 from AlgoLeadMe/24-SeongHoonC

24-SeongHoonC

SeongHoonC/README.md

@@ -24,5 +24,6 @@
 | 20차시 | 2024.04.07 | DP | <a href="https://www.acmicpc.net/problem/7579">앱</a> |https://github.com/AlgoLeadMe/AlgoLeadMe-6/pull/75 |
 | 21차시 | 2024.04.11 | DP | <a href="https://www.acmicpc.net/problem/1149">RGB거리</a> |https://github.com/AlgoLeadMe/AlgoLeadMe-6/pull/77 |
 | 22차시 | 2024.05.01 | DP | <a href="https://www.acmicpc.net/problem/11053">가장 긴 증가하는 부분 수열</a> |https://github.com/AlgoLeadMe/AlgoLeadMe-6/pull/80 |
-| 23차시 | 2024.05.14 | ??? | <a href="https://www.acmicpc.net/problem/1644">소수의 연속합</a> |https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/186 |
+| 23차시 | 2024.05.14 | 소수 | <a href="https://www.acmicpc.net/problem/1644">소수의 연속합</a> |https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/186 |
+| 24차시 | 2024.05.18| 백트래킹 | <a href="https://www.acmicpc.net/problem/9663">n-queen</a> |https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/192 |
 ---

SeongHoonC/dfs/nqeen.kt

@@ -0,0 +1,41 @@
+import java.io.BufferedReader
+import java.io.InputStreamReader
+
+var answer = 0
+var n: Int = 0
+lateinit var board: IntArray
+fun main() {
+    val br = BufferedReader(InputStreamReader(System.`in`))
+    n = br.readLine().toInt()
+    board = IntArray(n)
+    backTracking(0)
+    println(answer)
+}
+
+private fun backTracking(row: Int) {
+    // row 가 증가하다가 n 이랑 같아지면 정답 +1
+    if (row == n) {
+        answer++
+        return
+    }
+    // row 일 때 각 열에 놓을 경우의 수
+    for (col in 0 until n) {
+        board[row] = col
+        // 놓을 수 있다면 다음 행
+        if (check(row)) backTracking(row + 1)
+    }
+}
+
+private fun check(row: Int): Boolean {
+    for (i in 0 until row) {
+        // 행이 같거나
+        if (board[row] == board[i]) {
+            return false
+        }
+        // 대각선
+        if (row - i == kotlin.math.abs(board[row] - board[i])) {
+            return false
+        }
+    }
+    return true
+}