Merge pull request #2090 from CodingTestStudy2/이진희

[이진희] Day26

Author: github-actions[bot]

leetcode3/이진희/935. Knight Dialer.java

@@ -0,0 +1,47 @@
+import java.util.Arrays;
+
+class Solution {
+    private static final int MOD = 1_000_000_007;
+    private final int[][] moves = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+    
+    private int[][] memo;
+
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+
+        memo = new int[n + 1][10];
+        for (int[] row : memo) {
+            Arrays.fill(row, -1);
+        }
+
+        int totalWays = 0;
+     
+        for (int i = 0; i < 10; i++) {
+            totalWays = (totalWays + backtrack(n - 1, i)) % MOD;
+        }
+
+        return totalWays;
+    }
+
+    private int backtrack(int remain, int digit) {
+      
+        if (remain == 0) {
+            return 1;
+        }
+
+      
+        if (memo[remain][digit] != -1) {
+            return memo[remain][digit];
+        }
+
+        int count = 0;
+        for (int nextDigit : moves[digit]) {
+            count = (count + backtrack(remain - 1, nextDigit)) % MOD;
+        }
+
+        return memo[remain][digit] = count;
+    }
+}