fd

Author: dingjikerbo

leetcode/solution/src/CopyListWithRandomPointer.java

@@ -5,29 +5,26 @@ public class CopyListWithRandomPointer {
 
 
     public RandomListNode copyRandomList(RandomListNode head) {
-        for (RandomListNode node = head; node != null; ) {
-            RandomListNode next = node.next;
-
-            RandomListNode copy = new RandomListNode(node.label);
-            copy.next = next;
-            node.next = copy;
-            node = next;
+        for (RandomListNode p = head; p != null; ) {
+            RandomListNode next = p.next;
+            RandomListNode temp = new RandomListNode(p.label);
+            temp.next = p.next;
+            p.next = temp;
+            p = next;
         }
-
-        for (RandomListNode node = head; node != null; ) {
-            node.next.random = node.random != null ? node.random.next : null;
-            node = node.next.next;
+        for (RandomListNode p = head; p != null; ) {
+            if (p.random != null) {
+                p.next.random = p.random.next;
+            }
+            p = p.next.next;
         }
-
         RandomListNode dummy = new RandomListNode(0), cur = dummy;
-        for (RandomListNode node = head; node != null; ) {
-            cur.next = node.next;
+        for (RandomListNode p = head; p != null; ) {
+            cur.next = p.next;
             cur = cur.next;
-
-            node.next = node.next.next;
-            node = node.next;
+            p.next = p.next.next;
+            p = p.next;
         }
-
         return dummy.next;
     }
 }

leetcode/solution/src/LongestPalindromicSubstring.java

@@ -5,21 +5,26 @@ public class LongestPalindromicSubstring {
 
     private int begin, maxLen;
 
-    // 耗时14ms，平均复杂度O(n)
-    public String longestPalindrome(String s) {
+    // 耗时11ms，平均复杂度O(n)
+    public  String longestPalindrome(String s) {
+        int[] res = new int[2];
         for (int i = 0; i < s.length(); i++) {
-            helper(s, i, i);
-            helper(s, i, i + 1);
+            helper(s, i - 1, i + 1, res);
+            helper(s, i, i + 1, res);
         }
-        return s.substring(begin, begin + maxLen);
+        return s.substring(res[1], res[1] + res[0]);
     }
 
-    private void helper(String s, int i, int j) {
-        for (; i >= 0 && j < s.length() && s.charAt(i) == s.charAt(j); i--, j++) ;
-        int len = j - i - 1;
-        if (len > maxLen) {
-            maxLen = len;
-            begin = i + 1;
+    private void helper(String s, int left, int right, int[] res) {
+        for ( ; left >= 0 && right < s.length(); left--, right++) {
+            if (s.charAt(left) != s.charAt(right)) {
+                break;
+            }
+        }
+        int len = --right - ++left + 1;
+        if (len > res[0]) {
+            res[0] = len;
+            res[1] = left;
         }
     }
 

leetcode/src/Main.java

@@ -2,37 +2,69 @@
 
 public class Main {
 
-    public boolean isValid(String s) {
-        int[] stack = new int[s.length()];
-        int index = 0;
+    public  String longestPalindrome(String s) {
+        int[] res = new int[2];
         for (int i = 0; i < s.length(); i++) {
-            switch (s.charAt(i)) {
-                case '(':
-                case '[':
-                case '{':
-                    stack[index++] = i;
-                    break;
-                case ')':
-                    if (index == 0 || s.charAt(stack[--index]) != '(') {
-                        return false;
-                    }
-                    break;
-                case ']':
-                    if (index == 0 || s.charAt(stack[--index]) != '[') {
-                        return false;
-                    }
-                    break;
-                case '}':
-                    if (index == 0 || s.charAt(stack[--index]) != '{') {
-                        return false;
-                    }
-                    break;
+            helper(s, i - 1, i + 1, res);
+            helper(s, i, i + 1, res);
+        }
+        return s.substring(res[1], res[1] + res[0]);
+    }
+
+    private void helper(String s, int left, int right, int[] res) {
+        for ( ; left >= 0 && right < s.length(); left--, right++) {
+            if (s.charAt(left) != s.charAt(right)) {
+                break;
             }
         }
-        return index == 0;
+        int len = --right - ++left + 1;
+        if (len > res[0]) {
+            res[0] = len;
+            res[1] = left;
+        }
     }
 
-    public static void main(String[] args) {
+//    public static String longestPalindrome(String s) {
+//        if (s.length() == 0) {
+//            return "";
+//        }
+//        int max = 0, idx = -1;
+//        for (int i = 0; i < s.length(); i++) {
+//            int len = findLen(s, i);
+//            if (len > max) {
+//                max = len;
+//                idx = i;
+//            }
+//        }
+//        if (max % 2 == 0) {
+//            return s.substring(idx - max / 2 + 1, idx + max / 2 + 1);
+//        } else {
+//            return s.substring(idx - max / 2, idx + max / 2 + 1);
+//        }
+//    }
+//
+//    private static int findLen(String s, int index) {
+//        int len1 = 1;
+//        for (int i = 1; i <= s.length(); i++) {
+//            int i1 = index - i, i2 = index + i;
+//            if (i1 < 0 || i2 >= s.length() || s.charAt(i1) != s.charAt(i2)) {
+//                break;
+//            }
+//            len1 += 2;
+//        }
+//        int len2 = 0;
+//        for (int i = 0; i < s.length(); i++) {
+//            int i1 = index - i, i2 = index + i + 1;
+//            if (i1 < 0 || i2 >= s.length() || s.charAt(i1) != s.charAt(i2)) {
+//                break;
+//            }
+//            len2 += 2;
+//        }
+//        return Math.max(len1, len2);
+//    }
 
+    public static void main(String[] args) {
+        String s = longestPalindrome("cbbd");
+        System.out.println(s);
     }
 }