159 (1) two pointers window

stevencooks · stevencooks · commit 9b1793f30583 · 2015-09-30T16:10:57.000-04:00
diff --git a/src/_159_LongestSubstringWithAtMostTwoDistinctCharacters/Practice.java b/src/_159_LongestSubstringWithAtMostTwoDistinctCharacters/Practice.java
@@ -0,0 +1,24 @@
+/**
+ ***************************************************************************
+ * Description:
+ * 
+ * Given a string, find the length of the longest substring T that contains 
+ * at most 2 distinct characters. 
+ * 
+ * For example, Given s = “eceba”, T is "ece" which its length is 3.
+ * 
+ ***************************************************************************
+ * @tag : Hash Table; Two Pointers; String
+ * {@link https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/ }
+ */
+package _159_LongestSubstringWithAtMostTwoDistinctCharacters;
+
+/** see test {@link _159_LongestSubstringWithAtMostTwoDistinctCharacters.PracticeTest } */
+public class Practice {
+
+    public int lengthOfLongestSubstringTwoDistinct(String s) {
+        // TODO Auto-generated method stub
+        return 0;
+    }
+
+}
diff --git a/src/_159_LongestSubstringWithAtMostTwoDistinctCharacters/Solution.java b/src/_159_LongestSubstringWithAtMostTwoDistinctCharacters/Solution.java
@@ -0,0 +1,57 @@
+/**
+ * Time : O() ; Space: O()
+ * @tag : Hash Table; Two Pointers; String
+ * @by  : Steven Cooks
+ * @date: Sep 30, 2015
+ ***************************************************************************
+ * Description:
+ * 
+ * Given a string, find the length of the longest substring T that contains 
+ * at most 2 distinct characters. 
+ * 
+ * For example, Given s = “eceba”, T is "ece" which its length is 3.
+ * 
+ ***************************************************************************
+ * {@link https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/ }
+ */
+package _159_LongestSubstringWithAtMostTwoDistinctCharacters;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/** see test {@link _159_LongestSubstringWithAtMostTwoDistinctCharacters.SolutionTest } */
+public class Solution {
+    
+    public int lengthOfLongestSubstringTwoDistinct(String s) {
+        int res = 0;
+        // char, first appearance after the other char in current window
+        Map<Character, Integer> map = new HashMap<>();
+        int start = 0;
+        for (int i = 0; i < s.length(); i++) {
+            char ch = s.charAt(i);
+            if (map.size() < 2) {
+                // less than two characters in current window
+                if (!map.containsKey(ch)) {
+                    map.put(ch, i);
+                }
+            } else if (map.containsKey(ch)) {
+                // duplicates appears, update index
+                if (s.charAt(i - 1)  != ch) {
+                    map.put(ch, i);
+                }
+            } else {
+                // 3rd character appears
+                start = map.get(s.charAt(i - 1));
+                map = new HashMap<>();
+                map.put(s.charAt(i - 1), start);
+                map.put(ch, i);
+            }
+            // update global result
+            if (i - start + 1 > res) {
+                res = i - start + 1;
+            }
+        }
+        return res;
+    }
+
+}
diff --git a/test/_159_LongestSubstringWithAtMostTwoDistinctCharacters/PracticeTest.java b/test/_159_LongestSubstringWithAtMostTwoDistinctCharacters/PracticeTest.java
@@ -0,0 +1,69 @@
+package _159_LongestSubstringWithAtMostTwoDistinctCharacters;
+
+import static org.junit.Assert.*;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.Timeout;
+
+public class PracticeTest {
+    
+    /** Test method for {@link _159_LongestSubstringWithAtMostTwoDistinctCharacters.Practice } */
+    Practice solution;
+
+    @Rule
+    public Timeout globalTimeout = new Timeout(200);
+
+    @Before
+    public void setUp() throws Exception {
+        solution = new Practice();
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        solution = null;
+    }
+
+    @Test
+    public void Test1() {
+        String s = "eceba";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 3;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test2() {
+        String s = "aaaa";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 4;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test3() {
+        String s = "bbaabb";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 6;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test4() {
+        String s = "bbaabbc";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 6;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test5() {
+        String s = "bbacabbc";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 3;
+        assertEquals(expected, actual);
+    }
+
+}
diff --git a/test/_159_LongestSubstringWithAtMostTwoDistinctCharacters/SolutionTest.java b/test/_159_LongestSubstringWithAtMostTwoDistinctCharacters/SolutionTest.java
@@ -0,0 +1,69 @@
+package _159_LongestSubstringWithAtMostTwoDistinctCharacters;
+
+import static org.junit.Assert.*;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.Timeout;
+
+public class SolutionTest {
+    
+    /** Test method for {@link _159_LongestSubstringWithAtMostTwoDistinctCharacters.Solution } */
+    Solution solution;
+
+    @Rule
+    public Timeout globalTimeout = new Timeout(200);
+
+    @Before
+    public void setUp() throws Exception {
+        solution = new Solution();
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        solution = null;
+    }
+
+    @Test
+    public void Test1() {
+        String s = "eceba";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 3;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test2() {
+        String s = "aaaa";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 4;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test3() {
+        String s = "bbaabb";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 6;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test4() {
+        String s = "bbaabbc";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 6;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void Test5() {
+        String s = "bbacabbc";
+        int actual = solution.lengthOfLongestSubstringTwoDistinct(s);
+        int expected = 3;
+        assertEquals(expected, actual);
+    }
+
+}
