add: 016

Author: Blankj

README.md

@@ -75,6 +75,7 @@
 | 11   | [Container With Most Water][011]         | Array, Two Pointers              |
 | 12   | [Integer to Roman][012]                  | Math, String                     |
 | 15   | [3Sum][015]                              | Array, Two Pointers              |
+| 15   | [3Sum Closest][016]                      | Array, Two Pointers              |
 | 17   | [Letter Combinations of a Phone Number][017] | String, Backtracking             |
 | 19   | [Remove Nth Node From End of List][019]  | Linked List, Two Pointers        |
 | 33   | [Search in Rotated Sorted Array][033]    | Arrays, Binary Search            |
@@ -146,6 +147,7 @@
 [011]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/011/README.md
 [012]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/012/README.md
 [015]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/015/README.md
+[016]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/016/README.md
 [017]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/017/README.md
 [019]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/019/README.md
 [033]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/033/README.md

note/016/README.md

@@ -0,0 +1,54 @@
+# [3Sum Closest][title]
+
+## Description
+
+Given an array *S* of *n* integers, find three integers in *S* such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.
+
+```
+    For example, given array S = {-1 2 1 -4}, and target = 1.
+
+    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
+```
+
+**Tags:** Array, Two Pointers
+
+
+## 思路
+
+这道题和 [3Sum][015] 的思路基本一样，先对数组进行排序，然后遍历这个排序数组，用两个指针分别指向当前元素的下一个和数组尾部，判断三者的和与 `target` 的差值来移动两个指针，并更新其结果，当然，如果三者的和直接与 `target` 值相同，那么返回 `target` 结果即可。
+
+```java
+public class Solution {
+    public int threeSumClosest(int[] nums, int target) {
+        int delta = 0x7fffffff, res = 0;
+        Arrays.sort(nums);
+        int len = nums.length - 2;
+        for (int i = 0; i < len; i++) {
+            int st = i + 1, end = nums.length - 1;
+            while (st < end) {
+                int sum = nums[i] + nums[st] + nums[end];
+                int curDelta = Math.abs(sum - target);
+                if (curDelta == 0) return sum;
+                if (curDelta < delta) {
+                    delta = curDelta;
+                    res = sum;
+                }
+                if (sum > target) --end;
+                else ++st;
+            }
+        }
+        return res;
+    }
+}
+```
+
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-java-leetcode][ajl]
+
+
+
+[015]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/015/README.md
+[title]: https://leetcode.com/problems/3sum-closest
+[ajl]: https://github.com/Blankj/awesome-java-leetcode

src/com/blankj/medium/_016/Solution.java

@@ -0,0 +1,39 @@
+package com.blankj.medium._016;
+
+import java.util.Arrays;
+
+/**
+ * <pre>
+ *     author: Blankj
+ *     blog  : http://blankj.com
+ *     time  : 2018/01/25
+ *     desc  :
+ * </pre>
+ */
+public class Solution {
+    public int threeSumClosest(int[] nums, int target) {
+        int delta = 0x7fffffff, res = 0;
+        Arrays.sort(nums);
+        int len = nums.length - 2;
+        for (int i = 0; i < len; i++) {
+            int st = i + 1, end = nums.length - 1;
+            while (st < end) {
+                int sum = nums[i] + nums[st] + nums[end];
+                int curDelta = Math.abs(sum - target);
+                if (curDelta == 0) return sum;
+                if (curDelta < delta) {
+                    delta = curDelta;
+                    res = sum;
+                }
+                if (sum > target) --end;
+                else ++st;
+            }
+        }
+        return res;
+    }
+
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(solution.threeSumClosest(new int[]{-1, 2, 1, -4}, 1));
+    }
+}