409_Longest_Palindrome and 434_Number_of_Segments_in_a_String

README.md

@@ -123,10 +123,12 @@ Remember solutions are only solutions to given problems. If you want full study
 | 404 | [Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/404_Sum_of_Left_Leaves.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/404_Sum_of_Left_Leaves.java) | 1. Recursively DFS with root.left.left and root.left.right check<br>2. The same DFS based on stack |
 | 405 | [Convert a Number to Hexadecimal](https://leetcode.com/problems/convert-a-number-to-hexadecimal/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/405_Convert_a_Number_to_Hexadecimal.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/405_Convert_a_Number_to_Hexadecimal.java) | [Two's complement](https://en.wikipedia.org/wiki/Two%27s_complement) 1. Bit manipulate, each time handle 4 digits<br>2. Python (hex) and Java API (toHexString & Integer.toHexString) |
 | 408 | [Valid Word Abbreviation](https://leetcode.com/problems/valid-word-abbreviation/) &hearts; | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/408_Valid_Word_Abbreviation.py) | Go over abbr and word, O(n) and O(1) |
+| 409 | [Longest Palindrome](https://leetcode.com/problems/longest-palindrome/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/409_Longest_Palindrome.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/409_Longest_Palindrome.java) | Length of Palindrome is always 2n or 2n + 1. So, get all possible 2*n, and choose a single one as 1 if it exists. |
 | 412 | [Fizz Buzz](https://leetcode.com/problems/fizz-buzz/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/412_Fizz_Buzz.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/412_Fizz_Buzz.java) | 1. From 1 to n, condition check<br>2. Condition check and string connect |
 | 416 | [Partition Equal Subset Sum](https://leetcode.com/problems/partition-equal-subset-sum/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/416_Partition_Equal_Subset_Sum.py) | DP, Check if sum of some elements can be half of total sum, O(total_sum / 2 * n) and O(total_sum / 2) |
 | 421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/421_Maximum_XOR_of_Two_Numbers_in_an_Array.py) | Check 0~32 prefix, check if there is x y in prefixes, where x ^ y = answer ^ 1, O(32n) and O(n) |
 | 422 | [Valid Word Square](https://leetcode.com/problems/valid-word-square/) &hearts; | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/422_Valid_Word_Square.py) | Compare row with column, O(n^2) |
+| 434 | [Number of Segments in a String](https://leetcode.com/problems/number-of-segments-in-a-string/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/434_Number_of_Segments_in_a_String.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/434_Number_of_Segments_in_a_String.java) | 1. trim &split<br>2. Find segment in place |
 | 463 | [Island Perimeter](https://leetcode.com/problems/island-perimeter/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/463_Island_Perimeter.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/463_Island_Perimeter.java) | math, find the area, actual number, then find the digit |
 
 | # | To Understand |

java/409_Longest_Palindrome.java

@@ -0,0 +1,16 @@
+class Solution {
+    // https://leetcode.com/problems/longest-palindrome/solution/
+    public int longestPalindrome(String s) {
+        int[] count = new int[128];
+        for (char c: s.toCharArray())
+            count[c]++;
+
+        int ans = 0;
+        for (int v: count) {
+            ans += v / 2 * 2;
+            if (ans % 2 == 0 && v % 2 == 1)
+                ans++;
+        }
+        return ans;
+    }
+}

java/434_Number_of_Segments_in_a_String.java

@@ -0,0 +1,21 @@
+class Solution {
+    // https://leetcode.com/problems/number-of-segments-in-a-string/solution/
+    // public int countSegments(String s) {
+    //     String trimmed = s.trim();
+    //     if (trimmed.equals("")) {
+    //         return 0;
+    //     }
+    //     return trimmed.split("\\s+").length;
+    // }
+    public int countSegments(String s) {
+        int segmentCount = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            if ((i == 0 || s.charAt(i-1) == ' ') && s.charAt(i) != ' ') {
+                segmentCount++;
+            }
+        }
+
+        return segmentCount;
+    }
+}

python/409_Longest_Palindrome.py

@@ -0,0 +1,22 @@
+class Solution:
+    # https://leetcode.com/problems/longest-palindrome/solution/
+    # def longestPalindrome(self, s):
+    #     ans = 0
+    #     for v in collections.Counter(s).itervalues():
+    #         ans += v / 2 * 2
+    #         if ans % 2 == 0 and v % 2 == 1:
+    #             ans += 1
+    #     return ans
+    def longestPalindrome(self, s):
+        ans = 0
+        char_map = {}
+        for c in s:
+            char_map[c] = char_map.get(c, 0) + 1
+        for c in char_map.keys():
+            if char_map[c] % 2 == 0:
+                ans += char_map.pop(c)
+            else:
+                ans += char_map[c] / 2 * 2
+        if len(char_map) != 0:
+            ans += 1
+        return ans

python/434_Number_of_Segments_in_a_String.py

@@ -0,0 +1,16 @@
+class Solution(object):
+    # https://leetcode.com/problems/number-of-segments-in-a-string/solution/
+    # def countSegments(self, s):
+    #     """
+    #     :type s: str
+    #     :rtype: int
+    #     """
+    #     return len(s.split())
+
+    def countSegments(self, s):
+         segment_count = 0
+        for i in range(len(s)):
+            if (i == 0 or s[i-1] == ' ') and s[i] != ' ':
+                segment_count += 1
+
+        return segment_count