add leetcode: offer-19-49-60

Author: CodeWater404

Algorithm/src/offer/_19RegularExpressionMatching.java

@@ -0,0 +1,42 @@
+package offer;
+
+/**
+ * @author ： CodeWater
+ * @create ：2022-07-21-21:47
+ * @Function Description ：19.正则表达式匹配
+ */
+
+public class _19RegularExpressionMatching {
+    class Solution {
+        public boolean isMatch(String s, String p) {
+            int m = s.length() + 1 , n = p.length() + 1;
+            boolean[][] dp = new boolean[m][n];
+            dp[0][0] = true;
+            // 初始化首行
+            for( int j = 2 ; j < n ; j += 2 ){
+                dp[0][j] = dp[0][j - 2] && p.charAt( j - 1 ) == '*';
+            }
+
+            for( int i  = 1 ; i < m ; i++ ){
+                for( int j = 1 ; j < n ; j++ ){
+                    /*//==========================ifelse写法============================
+                    * if(p.charAt(j - 1) == '*') {
+                    if(dp[i][j - 2]) dp[i][j] = true;                                            // 1.
+                    else if(dp[i - 1][j] && s.charAt(i - 1) == p.charAt(j - 2)) dp[i][j] = true; // 2.
+                    else if(dp[i - 1][j] && p.charAt(j - 2) == '.') dp[i][j] = true;             // 3.
+                } else {
+                    if(dp[i - 1][j - 1] && s.charAt(i - 1) == p.charAt(j - 1)) dp[i][j] = true;  // 1.
+                    else if(dp[i - 1][j - 1] && p.charAt(j - 1) == '.') dp[i][j] = true;         // 2.
+                }
+                    * */
+                    dp[i][j] = p.charAt(j - 1) == '*' ?
+                            dp[i][j - 2] || dp[i - 1][j] && (s.charAt(i - 1) == p.charAt(j - 2) || p.charAt(j - 2) == '.') :
+                            dp[i - 1][j - 1] && (p.charAt(j - 1) == '.' || s.charAt(i - 1) == p.charAt(j - 1));
+
+                }
+            }
+
+            return dp[m - 1][n - 1];
+        }
+    }
+}

Algorithm/src/offer/_37SerializedBinaryTree.java

@@ -13,7 +13,7 @@ public class Codec {
         public String serialize(TreeNode root) {
             if(root == null) return "[]";
             StringBuilder res = new StringBuilder("[");
-            Queue<TreeNode> queue = new LinkedList<>() {{ add(root); }};
+            Queue<TreeNode> queue = new LinkedList<TreeNode>() {{ add(root); }};
             while(!queue.isEmpty()) {
                 TreeNode node = queue.poll();
                 if(node != null) {
@@ -32,7 +32,7 @@ public TreeNode deserialize(String data) {
             if(data.equals("[]")) return null;
             String[] vals = data.substring(1, data.length() - 1).split(",");
             TreeNode root = new TreeNode(Integer.parseInt(vals[0]));
-            Queue<TreeNode> queue = new LinkedList<>() {{ add(root); }};
+            Queue<TreeNode> queue = new LinkedList<TreeNode>() {{ add(root); }};
             int i = 1;
             while(!queue.isEmpty()) {
                 TreeNode node = queue.poll();

Algorithm/src/offer/_49UglyNumber.java

@@ -0,0 +1,27 @@
+package offer;
+
+/**
+ * @author ： CodeWater
+ * @create ：2022-07-21-23:32
+ * @Function Description ：49.丑数
+ */
+public class _49UglyNumber {
+    class Solution {
+        public int nthUglyNumber(int n) {
+            int a = 0 , b = 0 , c = 0 ;
+            int[] dp = new int[n];
+            dp[0] = 1;
+            for( int i = 1 ; i < n ; i++ ){
+                // 
+                int n2 = dp[a] * 2 , n3 = dp[b] * 3 , n5 = dp[c] * 5 ;
+                // 当前数是由上一个数乘三个因子相乘后结果的最小值
+                dp[i] = Math.min( Math.min( n2 , n3) , n5 );
+                // 看看最后结果是n2，n3，还是n5，相应的下标就加加
+                if( dp[i] == n2 ) a++;
+                if( dp[i] == n3 ) b++;
+                if( dp[i] == n5 ) c++;
+            }
+            return dp[n - 1];
+        }
+    }
+}

Algorithm/src/offer/_60NDicePoint.java

@@ -0,0 +1,28 @@
+package offer;
+
+import java.util.Arrays;
+
+/**
+ * @author ： CodeWater
+ * @create ：2022-07-21-23:43
+ * @Function Description ：60.n个骰子的点数
+ */
+public class _60NDicePoint {
+    class Solution {
+        public double[] dicesProbability(int n) {
+            double[] dp = new double[6];
+            Arrays.fill( dp , 1.0 / 6.0 );
+            for( int i = 2 ; i <= n ; i++ ){
+                double[] temp = new double[5 * i + 1];
+                for( int j = 0 ; j < dp.length ; j++ ){
+                    for( int k = 0 ; k < 6 ; k++ ){
+                        temp[j + k] += dp[j] / 6.0;
+                    }
+                }
+                dp = temp;
+            }
+
+            return dp;
+        }
+    }
+}