feat: add HashSet solution for leetcode #3

Author: Wang Dongxu

src/com/blankj/easy/_001/Solution.java

@@ -35,6 +35,31 @@ public int[] twoSum(int[] nums, int target) {
         return null;
     }
 
+    // Input array is sorted
+    // https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/description/
+    public int[] twoSumOrdered(int[] num, int target) {
+        int[] indice = new int[2];
+        if(num == null || num.length < 2) {
+            return indice; 
+        }
+        int left = 0;
+        int right = num.length - 1;
+        while(left < right) {
+            int sum = num[left] + num[right];
+            if(sum == target) {
+                indice[0] = left;
+                indice[1] = right;
+                return indice;
+            } else if(sum < target) {
+                left++;
+            } else {
+                right--; 
+            }
+
+        }
+        return indice;
+    }
+
     public static void main(String[] args) {
         Solution solution = new Solution();
         int[] nums = new int[]{2, 7, 11, 15};

src/com/blankj/medium/_003/HashSetSolution.java

@@ -0,0 +1,39 @@
+package com.blankj.medium._003;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Created by dash wang on 2/11/18.
+ * <p>
+ * HashSet + 双指针 问题
+ */
+public class HashSetSolution {
+    public int lengthOfLongestSubstring(String s) {
+        int len = s.length();
+        Set<Character> set = new HashSet<>();
+        int max = 0;
+        int head = 0, tail = 0;
+        for (head = 0; head < len; head++) {
+            // 出现重复, 移动尾指针,直到不重复为止
+            while (set.contains(s.charAt(head))) {
+                set.remove(s.charAt(tail));
+                tail++;
+            }
+            set.add(s.charAt(head));
+            int tempLen = head - tail + 1;
+            if (tempLen > max) {
+                max = tempLen;
+            }
+        }
+        return max;
+    }
+
+    public static void main(String[] args) {
+        HashSetSolution solution = new HashSetSolution();
+        System.out.println(solution.lengthOfLongestSubstring("abcabcbb"));
+        System.out.println(solution.lengthOfLongestSubstring("bbbbb"));
+        System.out.println(solution.lengthOfLongestSubstring("pwwkew"));
+        System.out.println(solution.lengthOfLongestSubstring("Abcabcbb"));
+    }
+}