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e720aa2d24
* Sync recent changes to the revised Word. * Revised the preface chapter * Revised the introduction chapter * Revised the computation complexity chapter * Revised the chapter data structure * Revised the chapter array and linked list * Revised the chapter stack and queue * Revised the chapter hashing * Revised the chapter tree * Revised the chapter heap * Revised the chapter graph * Revised the chapter searching * Reivised the sorting chapter * Revised the divide and conquer chapter * Revised the chapter backtacking * Revised the DP chapter * Revised the greedy chapter * Revised the appendix chapter * Revised the preface chapter doubly * Revised the figures
72 lines
2.2 KiB
C#
72 lines
2.2 KiB
C#
/**
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* File: coin_change.cs
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* Created Time: 2023-07-12
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* Author: hpstory (hpstory1024@163.com)
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*/
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namespace hello_algo.chapter_dynamic_programming;
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public class coin_change {
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/* 零钱兑换：动态规划 */
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int CoinChangeDP(int[] coins, int amt) {
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int n = coins.Length;
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int MAX = amt + 1;
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// 初始化 dp 表
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int[,] dp = new int[n + 1, amt + 1];
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// 状态转移：首行首列
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for (int a = 1; a <= amt; a++) {
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dp[0, a] = MAX;
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}
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// 状态转移：其余行和列
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for (int i = 1; i <= n; i++) {
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for (int a = 1; a <= amt; a++) {
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if (coins[i - 1] > a) {
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// 若超过目标金额，则不选硬币 i
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dp[i, a] = dp[i - 1, a];
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} else {
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// 不选和选硬币 i 这两种方案的较小值
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dp[i, a] = Math.Min(dp[i - 1, a], dp[i, a - coins[i - 1]] + 1);
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}
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}
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}
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return dp[n, amt] != MAX ? dp[n, amt] : -1;
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}
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/* 零钱兑换：空间优化后的动态规划 */
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int CoinChangeDPComp(int[] coins, int amt) {
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int n = coins.Length;
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int MAX = amt + 1;
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// 初始化 dp 表
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int[] dp = new int[amt + 1];
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Array.Fill(dp, MAX);
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dp[0] = 0;
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// 状态转移
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for (int i = 1; i <= n; i++) {
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for (int a = 1; a <= amt; a++) {
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if (coins[i - 1] > a) {
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// 若超过目标金额，则不选硬币 i
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dp[a] = dp[a];
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} else {
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// 不选和选硬币 i 这两种方案的较小值
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dp[a] = Math.Min(dp[a], dp[a - coins[i - 1]] + 1);
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}
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}
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}
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return dp[amt] != MAX ? dp[amt] : -1;
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}
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[Test]
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public void Test() {
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int[] coins = [1, 2, 5];
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int amt = 4;
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// 动态规划
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int res = CoinChangeDP(coins, amt);
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Console.WriteLine("凑到目标金额所需的最少硬币数量为 " + res);
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// 空间优化后的动态规划
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res = CoinChangeDPComp(coins, amt);
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Console.WriteLine("凑到目标金额所需的最少硬币数量为 " + res);
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}
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}
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