From 84fa669b79ebacc2b37843e4b572f6f20158076a Mon Sep 17 00:00:00 2001
From: "huangge1199@hotmail.com" <huangge1199>
Date: Fri, 23 Apr 2021 22:04:11 +0800
Subject: [PATCH] =?UTF-8?q?41:=E7=BC=BA=E5=A4=B1=E7=9A=84=E7=AC=AC?=
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---
 .../editor/cn/FirstMissingPositive.java       | 104 ++++++++++++++++++
 .../editor/cn/FirstMissingPositive.md         |  38 +++++++
 2 files changed, 142 insertions(+)
 create mode 100644 LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.java
 create mode 100644 LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.md

diff --git a/LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.java b/LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.java
new file mode 100644
index 0000000..c5d40f4
--- /dev/null
+++ b/LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.java
@@ -0,0 +1,104 @@
+//给你一个未排序的整数数组 nums ，请你找出其中没有出现的最小的正整数。 
+//
+// 
+//
+// 进阶：你可以实现时间复杂度为 O(n) 并且只使用常数级别额外空间的解决方案吗？ 
+//
+// 
+//
+// 示例 1： 
+//
+// 
+//输入：nums = [1,2,0]
+//输出：3
+// 
+//
+// 示例 2： 
+//
+// 
+//输入：nums = [3,4,-1,1]
+//输出：2
+// 
+//
+// 示例 3： 
+//
+// 
+//输入：nums = [7,8,9,11,12]
+//输出：1
+// 
+//
+// 
+//
+// 提示： 
+//
+// 
+// 0 <= nums.length <= 300 
+// -231 <= nums[i] <= 231 - 1 
+// 
+// Related Topics 数组 
+// 👍 1054 👎 0
+
+package leetcode.editor.cn;
+
+//41:缺失的第一个正数
+public class FirstMissingPositive {
+    public static void main(String[] args) {
+        //测试代码
+        Solution solution = new FirstMissingPositive().new Solution();
+        solution.firstMissingPositive(new int[]{1,2,0});
+    }
+
+    //力扣代码
+    //leetcode submit region begin(Prohibit modification and deletion)
+    class Solution {
+        public int firstMissingPositive(int[] nums) {
+            boolean is = true;
+            for (int i = 0; i < nums.length; i++) {
+                if (nums[i] == 1) {
+                    is = false;
+                }
+                if (nums[i] <= 0) {
+                    nums[i] = 1;
+                }
+            }
+            if (is) {
+                return 1;
+            }
+            for (int i = 0; i < nums.length; i++) {
+                if (Math.abs(nums[i]) <= nums.length && nums[Math.abs(nums[i]) - 1] > 0) {
+                    nums[Math.abs(nums[i]) - 1] *= -1;
+                }
+            }
+            for (int i = 1; i < nums.length; i++) {
+                if (nums[i] >= 0) {
+                    return i + 1;
+                }
+            }
+            return nums.length + 1;
+            //未完成的
+//            int index;
+//            for (int i = 0; i < nums.length; i++) {
+//                if (nums[i] == i) {
+//                    continue;
+//                }
+//                index = i;
+//                while (nums[index] != index && index >= 0 && index < nums.length) {
+//                    int temp = nums[nums[index]];
+//                    nums[nums[index]] = nums[index];
+//                    index = temp;
+//                }
+//                if (nums[index] == nums.length) {
+//                    nums[0] = nums[index];
+//                }
+//            }
+//            for (int i = 1; i < nums.length; i++) {
+//                if (nums[i] != i) {
+//                    return i;
+//                }
+//            }
+//            return nums[0] == nums.length ? nums.length + 1 : nums.length;
+        }
+    }
+//leetcode submit region end(Prohibit modification and deletion)
+
+}
\ No newline at end of file
diff --git a/LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.md b/LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.md
new file mode 100644
index 0000000..623ce31
--- /dev/null
+++ b/LeetCode/src/main/java/leetcode/editor/cn/FirstMissingPositive.md
@@ -0,0 +1,38 @@
+<p>给你一个未排序的整数数组 <code>nums</code> ，请你找出其中没有出现的最小的正整数。</p>
+
+<p> </p>
+
+<p><strong>进阶：</strong>你可以实现时间复杂度为 <code>O(n)</code> 并且只使用常数级别额外空间的解决方案吗？</p>
+
+<p> </p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre>
+<strong>输入：</strong>nums = [1,2,0]
+<strong>输出：</strong>3
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<strong>输入：</strong>nums = [3,4,-1,1]
+<strong>输出：</strong>2
+</pre>
+
+<p><strong>示例 3：</strong></p>
+
+<pre>
+<strong>输入：</strong>nums = [7,8,9,11,12]
+<strong>输出：</strong>1
+</pre>
+
+<p> </p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>0 <= nums.length <= 300</code></li>
+	<li><code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code></li>
+</ul>
+<div><div>Related Topics</div><div><li>数组</li></div></div>\n<div><li>👍 1054</li><li>👎 0</li></div>
\ No newline at end of file