From a25d2e91fb12ed4be8772c73d7fdcb6a97c37d6d Mon Sep 17 00:00:00 2001
From: YDZ <ydz627@gmail.com>
Date: Tue, 7 May 2019 19:04:24 +0400
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20problem=20219?=
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---
 .../219. Contains Duplicate II.go             | 21 ++++++++
 .../219. Contains Duplicate II_test.go        | 53 +++++++++++++++++++
 .../219. Contains Duplicate II/README.md      | 32 +++++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 Algorithms/219. Contains Duplicate II/219. Contains Duplicate II.go
 create mode 100644 Algorithms/219. Contains Duplicate II/219. Contains Duplicate II_test.go
 create mode 100644 Algorithms/219. Contains Duplicate II/README.md

diff --git a/Algorithms/219. Contains Duplicate II/219. Contains Duplicate II.go b/Algorithms/219. Contains Duplicate II/219. Contains Duplicate II.go
new file mode 100644
index 00000000..5cacd0e4
--- /dev/null
+++ b/Algorithms/219. Contains Duplicate II/219. Contains Duplicate II.go	
@@ -0,0 +1,21 @@
+package leetcode
+
+func containsNearbyDuplicate(nums []int, k int) bool {
+	if len(nums) <= 1 {
+		return false
+	}
+	if k <= 0 {
+		return false
+	}
+	record := make(map[int]bool, len(nums))
+	for i, n := range nums {
+		if _, found := record[n]; found {
+			return true
+		}
+		record[n] = true
+		if len(record) == k+1 {
+			delete(record, nums[i-k])
+		}
+	}
+	return false
+}
diff --git a/Algorithms/219. Contains Duplicate II/219. Contains Duplicate II_test.go b/Algorithms/219. Contains Duplicate II/219. Contains Duplicate II_test.go
new file mode 100644
index 00000000..e666345b
--- /dev/null
+++ b/Algorithms/219. Contains Duplicate II/219. Contains Duplicate II_test.go	
@@ -0,0 +1,53 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question219 struct {
+	para219
+	ans219
+}
+
+// para 是参数
+// one 代表第一个参数
+type para219 struct {
+	one []int
+	k   int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans219 struct {
+	one bool
+}
+
+func Test_Problem219(t *testing.T) {
+
+	qs := []question219{
+
+		question219{
+			para219{[]int{1, 2, 3, 1}, 3},
+			ans219{true},
+		},
+
+		question219{
+			para219{[]int{1, 0, 0, 1}, 1},
+			ans219{true},
+		},
+
+		question219{
+			para219{[]int{1, 2, 3, 1, 2, 3}, 2},
+			ans219{false},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 219------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans219, q.para219
+		fmt.Printf("【input】:%v       【output】:%v\n", p, containsNearbyDuplicate(p.one, p.k))
+	}
+	fmt.Printf("\n\n\n")
+}
diff --git a/Algorithms/219. Contains Duplicate II/README.md b/Algorithms/219. Contains Duplicate II/README.md
new file mode 100644
index 00000000..a3ba3174
--- /dev/null
+++ b/Algorithms/219. Contains Duplicate II/README.md	
@@ -0,0 +1,32 @@
+# [219. Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/)
+
+## 题目
+
+Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.
+
+
+Example 1:
+
+```c
+Input: nums = [1,2,3,1], k = 3
+Output: true
+```
+Example 2:
+
+```c
+Input: nums = [1,0,1,1], k = 1
+Output: true
+```
+
+Example 3:
+
+```c
+Input: nums = [1,2,3,1,2,3], k = 2
+Output: false
+```
+
+## 题目大意
+
+这是一道简单题，如果数组里面有重复数字，并且重复数字的下标差值小于等于 K 就输出 true，如果没有重复数字或者下标差值超过了 K ，则输出 flase。
+
+这道题可以维护一个只有 K 个元素的 map，每次只需要判断这个 map 里面是否存在这个元素即可。如果存在就代表重复数字的下标差值在 K 以内。map 的长度如果超过了 K 以后就删除掉 i-k 的那个元素，这样一直维护 map 里面只有 K 个元素。