From b00057e39f829451323a86fb22610ac4d13a321b Mon Sep 17 00:00:00 2001
From: "huangge1199@hotmail.com" <huangge1199>
Date: Sun, 15 Aug 2021 19:53:20 +0800
Subject: [PATCH] =?UTF-8?q?400:=E7=AC=AC=20N=20=E4=BD=8D=E6=95=B0=E5=AD=97?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/leetcode/editor/cn/NthDigit.java     | 52 +++++++++++++++++++
 src/main/java/leetcode/editor/cn/NthDigit.md  | 23 ++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 src/main/java/leetcode/editor/cn/NthDigit.java
 create mode 100644 src/main/java/leetcode/editor/cn/NthDigit.md

diff --git a/src/main/java/leetcode/editor/cn/NthDigit.java b/src/main/java/leetcode/editor/cn/NthDigit.java
new file mode 100644
index 0000000..81c2d68
--- /dev/null
+++ b/src/main/java/leetcode/editor/cn/NthDigit.java
@@ -0,0 +1,52 @@
+//在无限的整数序列 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...中找到第 n 位数字。 
+//
+// 
+//
+// 注意：n 是正数且在 32 位整数范围内（n < 231）。 
+//
+// 
+//
+// 示例 1： 
+//
+// 
+//输入：3
+//输出：3
+// 
+//
+// 示例 2： 
+//
+// 
+//输入：11
+//输出：0
+//解释：第 11 位数字在序列 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ... 里是 0 ，它是 10 的一部分。
+// 
+// Related Topics 数学 二分查找 
+// 👍 170 👎 0
+
+package leetcode.editor.cn;
+//400:第 N 位数字
+class NthDigit{
+    public static void main(String[] args) {
+        //测试代码
+        Solution solution = new NthDigit().new Solution();
+    }
+    
+    //力扣代码
+    //leetcode submit region begin(Prohibit modification and deletion)
+class Solution {
+    public int findNthDigit(int n) {
+        int[] ant = new int[]{0, 10, 190, 2890, 38890, 488890, 5888890, 68888890, 788888890};
+        int[] numBegin = new int[]{0, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000};
+        for(int i = ant.length - 1; i >= 0; i--){
+            if(n >= ant[i]){
+                int num = (n - ant[i]) / (i + 1) + numBegin[i];
+                int posi = (n - ant[i]) % (i + 1);
+                return num % (int)Math.pow(10, i + 1 - posi) / (int)Math.pow(10,  i - posi);
+            }
+        }
+        return 0;
+    }
+}
+//leetcode submit region end(Prohibit modification and deletion)
+
+}
\ No newline at end of file
diff --git a/src/main/java/leetcode/editor/cn/NthDigit.md b/src/main/java/leetcode/editor/cn/NthDigit.md
new file mode 100644
index 0000000..4896cba
--- /dev/null
+++ b/src/main/java/leetcode/editor/cn/NthDigit.md
@@ -0,0 +1,23 @@
+<p>在无限的整数序列 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...中找到第 <code>n</code><em> </em>位数字。</p>
+
+<p> </p>
+
+<p><strong>注意：</strong><code>n</code><em> </em>是正数且在 32 位整数范围内（<code>n < 2<sup>31</sup></code>）。</p>
+
+<p> </p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre>
+<strong>输入：</strong>3
+<strong>输出：</strong>3
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<strong>输入：</strong>11
+<strong>输出：</strong>0
+<strong>解释：</strong>第 11 位数字在序列 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ... 里是 <strong>0 </strong>，它是 10 的一部分。
+</pre>
+<div><div>Related Topics</div><div><li>数学</li><li>二分查找</li></div></div>\n<div><li>👍 170</li><li>👎 0</li></div>
\ No newline at end of file