hot100数组

.gitignore

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+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+/.idea
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.cool</groupId>
+    <artifactId>LeetCode</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <dependencies>
+
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.2</version>
+        </dependency>
+    </dependencies>
+
+</project>

src/main/java/com/cool/Main.java

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+package com.cool;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello world!");
+    }
+}

src/main/java/com/cool/Template.java

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+package com.cool;
+
+public class Template {
+
+    /**
+     * Date 2924/8/19
+     * DayNumber 1/2/3/4
+     * @param template
+     */
+    public void test(int template){
+
+    }
+
+}

src/main/java/com/cool/hot100/common_arr/Num189.java

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+package com.cool.hot100.common_arr;
+
+public class Num189 {
+
+
+    /**
+     * Date 2024/8/19
+     * DayNumber 2
+     */
+    public void rotate(int[] nums, int k) {
+//
+//        int[] newArr = new int[nums.length];
+//        for (int i = 0; i < newArr.length; i++) {
+//            newArr[(i + k)%nums.length] = nums[i];
+//        }
+//        System.arraycopy(newArr,0,nums,0,nums.length);
+        reverse(nums,0,nums.length-1);
+        reverse(nums,0,k%nums.length-1);
+        reverse(nums,k%nums.length,nums.length-1);
+
+    }
+
+    public void reverse(int[]nums,int start,int end){
+        while(start<end){
+            int temp=nums[end];
+            nums[end]=nums[start];
+            nums[start]=temp;
+            start++;
+            end--;
+        }
+    }
+}

src/main/java/com/cool/hot100/common_arr/Num238.java

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+package com.cool.hot100.common_arr;
+
+public class Num238 {
+
+    /**
+     * Date 2024/8/19
+     * DayNumber 3
+     *
+     * @param nums
+     * @return
+     */
+    public int[] productExceptSelf(int[] nums) {
+        int n = nums.length;
+        int[] lArr = new int[n];
+        int[] rArr = new int[n];
+        lArr[0] = 1;
+        rArr[n - 1] = 1;
+        for (int i = 1; i < n; i++) {
+            lArr[i] = lArr[i - 1] * nums[i - 1];
+//            rArr[n - i - 1] = rArr[n - i] * nums[n - i];
+        }
+        int R = 1;
+        for (int i = n - 2; i >= 0; i--) {
+            R *= nums[i + 1];
+            lArr[i] *= R;
+        }
+        return lArr;
+    }
+}

src/main/java/com/cool/hot100/common_arr/Num41.java

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+package com.cool.hot100.common_arr;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+
+public class Num41 {
+
+
+    /**
+     * DayNumber 4
+     * Date 2024/8/19
+     */
+    public int firstMissingPositive(int[] nums) {
+//        Arrays.sort(nums);
+//        int R=1;
+//        for (int num : nums) {
+//            if(num>0){
+//                if(num>R){
+//                    return R;
+//                }else if(num==R) {
+//                    R++;
+//                }
+//            }
+//        }
+//        return R;
+        int n = nums.length;
+        for (int i = 0; i < n; ++i) {
+            if (nums[i] <= 0) {
+                nums[i] = n + 1;
+            }
+        }
+        for (int i = 0; i < n; i++) {
+            int num = Math.abs(nums[i]);
+            if (num <= n) {
+                nums[num - 1] = -Math.abs(nums[num - 1]);
+            }
+        }
+        for (int i = 0; i < n; i++) {
+            if (nums[i] > 0) {
+                return i + 1;
+            }
+        }
+        return n + 1;
+    }
+
+    @Test
+    public void test() {
+        System.out.println(firstMissingPositive(new int[]{1, 1}));
+    }
+}

src/main/java/com/cool/hot100/common_arr/Num53.java

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+package com.cool.hot100.common_arr;
+
+import org.junit.Test;
+
+public class Num53 {
+
+    /**
+     * 53. 最大子序和
+     */
+    /**
+     * 给你一个整数数组 nums ，请你找出一个具有最大和的连续子数组（子数组最少包含一个元素），返回其最大和。
+     * 子数组
+     * 是数组中的一个连续部分。
+     * 示例 1：
+     * 输入：nums = [-2,1,-3,4,-1,2,1,-5,4]
+     * 输出：6
+     * 解释：连续子数组 [4,-1,2,1] 的和最大，为 6 。
+     * 示例 2：
+     * 输入：nums = [1]
+     * 输出：1
+     * 示例 3：
+     * 输入：nums = [5,4,-1,7,8]
+     * 输出：23
+     *
+     * @param nums
+     * @return
+     */
+
+    public int maxSubArray(int[] nums) {
+        int left = 0;
+        int right = 0;
+        int res = Integer.MIN_VALUE;
+        int sum = 0;
+        while (right < nums.length) {
+            sum += nums[right++];
+            if (sum >= 0) {
+            } else {
+                sum = 0;
+            }
+            res = Math.max(sum, res);
+        }
+        return res;
+    }
+
+    @Test
+    public void test() {
+        System.out.println(maxSubArray(new int[]{-2, 1, -3, 4, -1, 2, 1, -5, 4}));
+    }
+
+
+}

src/main/java/com/cool/hot100/common_arr/Num56.java

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+package com.cool.hot100.common_arr;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Num56 {
+
+
+    /**
+     * Date 2024/8/19
+     * DayNumber 1
+     * 以数组 intervals 表示若干个区间的集合，其中单个区间为 intervals[i] = [starti, endi] 。请你合并所有重叠的区间，并返回 一个不重叠的区间数组，该数组需恰好覆盖输入中的所有区间 。
+     * 示例 1：
+     * 输入：intervals = [[1,3],[2,6],[8,10],[15,18]]
+     * 输出：[[1,6],[8,10],[15,18]]
+     * 解释：区间 [1,3] 和 [2,6] 重叠, 将它们合并为 [1,6].
+     * 示例 2：
+     * 输入：intervals = [[1,4],[4,5]]
+     * 输出：[[1,5]]
+     * 解释：区间 [1,4] 和 [4,5] 可被视为重叠区间。
+     */
+    public int[][] merge(int[][] intervals) {
+        Arrays.sort(intervals, (p, q) -> p[0] - q[0]); // 按照左端点从小到大排序
+        List<int[]> list=new ArrayList<>();
+        list.add(intervals[0]);
+        for (int[] interval : intervals) {
+            int index = list.size() - 1;
+            if (list.get(index)[1] < interval[0]) {
+                list.add(interval);
+            } else {
+                list.get(index)[1] = Math.max(list.get(index)[1], interval[1]);
+            }
+
+        }
+        return list.toArray(new int[list.size()][]);
+    }
+
+
+    @Test
+    public void test(){
+        merge(new int[][]{{2,3},{2,2},{3,3},{1,3},{5,7},{2,2},{4,6}});
+    }
+}