From 8f722ebb0cd75c7bb7c1d09a0bf24c632eb2e937 Mon Sep 17 00:00:00 2001 From: whaifree <49432110+whaibetter@users.noreply.github.com> Date: Thu, 22 Aug 2024 00:43:33 +0800 Subject: [PATCH] =?UTF-8?q?feat(leetcode):=20=E6=B7=BB=E5=8A=A0=E6=96=B0?= =?UTF-8?q?=E7=9A=84=E7=AE=97=E6=B3=95=E9=A2=98=E7=9B=AE=E5=AE=9E=E7=8E=B0?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit - 实现LeetCode322 题目：零钱兑换。提供了一个Solution类，使用动态规划算法计算最少的硬币数量。 - 实现LeetCode 377 题目：组合总和IV。提供了一个Solution类，使用动态规划算法计算组合的总数。 - 实现LeetCode 快速排序。提供了一个Solution类，包含一个快速排序算法，能够对数组进行排序。各题目实现均通过测试验证。 --- .../cn/whaifree/redo/redoAll/LeetCode322.java | 54 +++++++++++++++++ .../cn/whaifree/redo/redoAll/LeetCode377.java | 59 +++++++++++++++++++ .../redo/redoAll/LeetCodeQuickSort.java | 57 ++++++++++++++++++ 3 files changed, 170 insertions(+) create mode 100644 src/main/java/cn/whaifree/redo/redoAll/LeetCode322.java create mode 100644 src/main/java/cn/whaifree/redo/redoAll/LeetCode377.java create mode 100644 src/main/java/cn/whaifree/redo/redoAll/LeetCodeQuickSort.java diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode322.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode322.java new file mode 100644 index 0000000..ecdbd8b --- /dev/null +++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode322.java @@ -0,0 +1,54 @@ +package cn.whaifree.redo.redoAll; + +import org.junit.Test; + +/** + * @version 1.0 + * @Author whai文海 + * @Date 2024/8/21 23:53 + * @注释 + */ +public class LeetCode322 { + + @Test + public void test() { + int[] coins = {2}; + int amount = 3; + Solution solution = new Solution(); + int i = solution.coinChange(coins, amount); + System.out.println(i); + } + + class Solution { + + /** + * dp[j] 表示从0-i中随便取，满足j个背包容量的最少个数 + * + * 0 1 2 3 4 5 6 7 8 9 10 11 + * 1 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11] + * 2 [0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6] + * 5 [0, 1, 1, 2, 2, 1, 2, 2, 3, 3, 2, 3] + * + * @param coins + * @param amount + * @return + */ + public int coinChange(int[] coins, int amount) { + + + int[] dp = new int[amount + 1]; + for (int i = 1; i <= amount; i++) { + dp[i] = Integer.MAX_VALUE; + } + dp[0] = 0; + for (int i = 0; i < coins.length; i++) { + for (int j = coins[i]; j <= amount; j++) { + if (dp[j - coins[i]] != Integer.MAX_VALUE) { + dp[j] = Math.min(dp[j], dp[j - coins[i]] + 1); + } + } + } + return dp[amount] == Integer.MAX_VALUE ? -1 : dp[amount]; + } + } +} diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode377.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode377.java new file mode 100644 index 0000000..2ef0e2a --- /dev/null +++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode377.java @@ -0,0 +1,59 @@ +package cn.whaifree.redo.redoAll; + +import org.junit.Test; + +/** + * @version 1.0 + * @Author whai文海 + * @Date 2024/8/22 0:14 + * @注释 + */ +public class LeetCode377 { + + @Test + public void test() { + int[] nums = {1, 2, 3}; + int target = 4; + Solution solution = new Solution(); + System.out.println(solution.combinationSum4(nums, target)); + + } + class Solution { + /** + * dp[i] 表示 + * + * @param nums + * @param target + * @return + */ + public int combinationSum4(int[] nums, int target) { + + /** + * 如果我们先遍历物品（nums），再遍历背包（target），那么我们实际上是在考虑每个物品对每个目标值的贡献。 + * 这种方式会忽略组合的顺序，即它只考虑了物品的组合，而不考虑这些物品的排列顺序。 + * - 确定一个物品，就不会关注他的顺序 + * + * 例如，对于目标值4，如果我们先遍历物品， + * 可能会得到组合{1,3}，但不会得到组合{3,1}，因为这种方式只考虑了物品的组合，而不考虑排列。 + */ + int[] dp = new int[target + 1]; + dp[0] = 1; // 都不放入 情况有一种 + for (int j = 1; j < target + 1; j++) { + for (int i = 0; i < nums.length; i++) { + if (j >= nums[i]) { + dp[j] = dp[j] + dp[j - nums[i]]; + // dp[j] 不放 + // dp[j - nums[i]] 放，放也有多种情况 + } + } + /** + * 如果把遍历nums（物品）放在外循环， + * 遍历target的作为内循环的话，举一个例子： + * 计算dp[4]的时候，结果集只有 {1,3} 这样的集合，忽略了{3,1} + */ + } + + return dp[target]; + } + } +} diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCodeQuickSort.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCodeQuickSort.java new file mode 100644 index 0000000..514be88 --- /dev/null +++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCodeQuickSort.java @@ -0,0 +1,57 @@ +package cn.whaifree.redo.redoAll; + +import java.util.Arrays; +import java.util.Random; + +/** + * @version 1.0 + * @Author whai文海 + * @Date 2024/8/21 22:30 + * @注释 + */ +public class LeetCodeQuickSort { + public static void main(String[] args) { + System.out.println(Arrays.toString(new LeetCodeQuickSort().new Solution().sortArray(new int[]{110, 100, 0}))); + } + + class Solution { + public int[] sortArray(int[] nums) { + sort(nums, 0, nums.length - 1); + return nums; + } + public static void sort(int[] nums, int leftIndex, int rightIndex) { + if (leftIndex >= rightIndex) { + return; + } + // ! 随机挑选一个幸运儿 + int q = new Random().nextInt(rightIndex - leftIndex + 1) + leftIndex; + swap(nums, leftIndex, q); + + int pivot = nums[leftIndex]; + int l = leftIndex; + int r = rightIndex; + while (l < r) { + while (l < r && nums[r] >= pivot) { + r--; + } + while (l < r && nums[l] <= pivot) { + l++; + } + swap(nums, l, r); + } + swap(nums, l, leftIndex); + sort(nums, leftIndex, l - 1); + sort(nums, r + 1, rightIndex); + } + + public static void swap(int[] nums, int i, int j) { + int temp = nums[i]; + nums[i] = nums[j]; + nums[j] = temp; + } + } + + + + +}