add 340

Author: fishercoder1534

README.md

@@ -214,6 +214,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |344|[Reverse String](https://leetcode.com/problems/reverse-string/)|[Solution](../master/src/main/java/com/fishercoder/solutions/ReverseString.java) | O(n) |O(1) | Easy | String
 |343|[Integer Break](https://leetcode.com/problems/integer-break/)|[Solution](../master/src/main/java/com/fishercoder/solutions/IntegerBreak.java)| O(1)|O(1) | Medium| Math
 |341|[Flatten Nested List Iterator](https://leetcode.com/problems/flatten-nested-list-iterator/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_341.java)| O(n)|O(n) | Medium| Stack
+|340|[Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_340.java)| O(n)|O(1) | Hard| Sliding Window
 |339|[Nested List Weight Sum](https://leetcode.com/problems/nested-list-weight-sum/)|[Solution](../master/src/main/java/com/fishercoder/solutions/NestedListWeightSum.java)| O(n)|O(h)) | Easy| DFS
 |338|[Counting Bits](https://leetcode.com/problems/counting-bits/)|[Solution](../master/src/main/java/com/fishercoder/solutions/CountingBits.java)| O(nlogn)|O(h) | Medium| 
 |337|[House Robber III](https://leetcode.com/problems/house-robber-iii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_337.java)| O(n)|O(n)| Medium | DP

src/main/java/com/fishercoder/solutions/_340.java

@@ -0,0 +1,34 @@
+package com.fishercoder.solutions;
+
+/**
+ * 340. Longest Substring with At Most K Distinct Characters
+ *
+ * Given a string, find the length of the longest substring T that contains at most k distinct characters.
+
+ For example, Given s = “eceba” and k = 2,
+
+ T is "ece" which its length is 3.
+
+ */
+public class _340 {
+
+    /**credit: https://discuss.leetcode.com/topic/41671/15-lines-java-solution-using-slide-window*/
+    public int lengthOfLongestSubstringKDistinct(String s, int k) {
+        int[] count = new int[256];
+        int left = 0;
+        int result = 0;
+        int num = 0;
+        for (int right = 0; right < s.length(); right++) {
+            if (count[s.charAt(right)]++ == 0) {
+                num++;
+            }
+            if (num > k) {
+                while (--count[s.charAt(left++)] > 0);
+                num--;
+            }
+            result = Math.max(result, right - left + 1);
+        }
+        return result;
+    }
+
+}

src/test/java/com/fishercoder/_340Test.java

@@ -0,0 +1,55 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._340;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Created by stevesun on 6/10/17.
+ */
+public class _340Test {
+    private static _340 test;
+
+    @BeforeClass
+    public static void setup(){
+        test = new _340();
+    }
+
+    @Test
+    public void test1(){
+        assertEquals(3, test.lengthOfLongestSubstringKDistinct("eceba", 2));
+    }
+
+    @Test
+    public void test2(){
+        assertEquals(0, test.lengthOfLongestSubstringKDistinct("", 0));
+    }
+
+    @Test
+    public void test3(){
+        assertEquals(0, test.lengthOfLongestSubstringKDistinct("a", 0));
+    }
+
+    @Test
+    public void test4(){
+        assertEquals(1, test.lengthOfLongestSubstringKDistinct("a", 1));
+    }
+
+    @Test
+    public void test5(){
+        assertEquals(1, test.lengthOfLongestSubstringKDistinct("a", 2));
+    }
+
+    @Test
+    public void test6(){
+        assertEquals(2, test.lengthOfLongestSubstringKDistinct("aa", 1));
+    }
+
+    @Test
+    public void test7(){
+        assertEquals(3, test.lengthOfLongestSubstringKDistinct("bacc", 2));
+    }
+
+}