From f96f58377163444c0970487e65ff55aa7fb6ff4d Mon Sep 17 00:00:00 2001
From: Justin Tse <xief008@outlook.com>
Date: Sat, 2 Sep 2023 20:20:17 +0800
Subject: [PATCH] Add Chapter greedy for JS and TS code (#718)

* Fix binary_search_tree TS code

* Update binary_search_tree js code style

* Add the JavaScript code for Chapter of Greedy

* Add the TypeScript code for Chapter of Greedy

---------

Co-authored-by: Yudong Jin <krahets@163.com>
---
 .../chapter_greedy/coin_change_greedy.js      | 48 ++++++++++++++++++
 .../chapter_greedy/fractional_knapsack.js     | 46 +++++++++++++++++
 .../javascript/chapter_greedy/max_capacity.js | 33 ++++++++++++
 .../chapter_greedy/max_product_cutting.js     | 33 ++++++++++++
 .../chapter_greedy/coin_change_greedy.ts      | 50 +++++++++++++++++++
 .../chapter_greedy/fractional_knapsack.ts     | 50 +++++++++++++++++++
 .../typescript/chapter_greedy/max_capacity.ts | 35 +++++++++++++
 .../chapter_greedy/max_product_cutting.ts     | 35 +++++++++++++
 8 files changed, 330 insertions(+)
 create mode 100644 codes/javascript/chapter_greedy/coin_change_greedy.js
 create mode 100644 codes/javascript/chapter_greedy/fractional_knapsack.js
 create mode 100644 codes/javascript/chapter_greedy/max_capacity.js
 create mode 100644 codes/javascript/chapter_greedy/max_product_cutting.js
 create mode 100644 codes/typescript/chapter_greedy/coin_change_greedy.ts
 create mode 100644 codes/typescript/chapter_greedy/fractional_knapsack.ts
 create mode 100644 codes/typescript/chapter_greedy/max_capacity.ts
 create mode 100644 codes/typescript/chapter_greedy/max_product_cutting.ts

diff --git a/codes/javascript/chapter_greedy/coin_change_greedy.js b/codes/javascript/chapter_greedy/coin_change_greedy.js
new file mode 100644
index 000000000..4be23dfeb
--- /dev/null
+++ b/codes/javascript/chapter_greedy/coin_change_greedy.js
@@ -0,0 +1,48 @@
+/**
+ * File: coin_change_greedy.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 零钱兑换：贪心 */
+function coin_change_greedy(coins, amt) {
+    // 假设 coins 数组有序
+    let i = coins.length - 1;
+    let count = 0;
+    // 循环进行贪心选择，直到无剩余金额
+    while (amt > 0) {
+        // 找到小于且最接近剩余金额的硬币
+        while (i > 0 && coins[i] > amt) {
+            i--;
+        }
+        // 选择 coins[i]
+        amt -= coins[i];
+        count++;
+    }
+    // 若未找到可行方案，则返回 -1
+    return amt === 0 ? count : -1;
+}
+
+/* Driver Code */
+// 贪心：能够保证找到全局最优解
+let coins = [1, 5, 10, 20, 50, 100];
+let amt = 186;
+let res = coin_change_greedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`凑到 ${amt} 所需的最少硬币数量为 ${res}`);
+
+// 贪心：无法保证找到全局最优解
+coins = [1, 20, 50];
+amt = 60;
+res = coin_change_greedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`凑到 ${amt} 所需的最少硬币数量为 ${res}`);
+console.log("实际上需要的最少数量为 3 ，即 20 + 20 + 20");
+
+// 贪心：无法保证找到全局最优解
+coins = [1, 49, 50];
+amt = 98;
+res = coin_change_greedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`凑到 ${amt} 所需的最少硬币数量为 ${res}`);
+console.log("实际上需要的最少数量为 2 ，即 49 + 49");
diff --git a/codes/javascript/chapter_greedy/fractional_knapsack.js b/codes/javascript/chapter_greedy/fractional_knapsack.js
new file mode 100644
index 000000000..a09b19a79
--- /dev/null
+++ b/codes/javascript/chapter_greedy/fractional_knapsack.js
@@ -0,0 +1,46 @@
+/**
+ * File: fractional_knapsack.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 物品 */
+class Item {
+    constructor(w, v) {
+        this.w = w; // 物品重量
+        this.v = v; // 物品价值
+    }
+}
+
+/* 分数背包：贪心 */
+function fractional_knapsack(wgt, val, cap) {
+    // 创建物品列表，包含两个属性：重量、价值
+    const items = wgt.map((w, i) => new Item(w, val[i]));
+    // 按照单位价值 item.v / item.w 从高到低进行排序
+    items.sort((a, b) => (b.v / b.w) - (a.v / a.w));
+    // 循环贪心选择
+    let res = 0;
+    for (const item of items) {
+        if (item.w <= cap) {
+            // 若剩余容量充足，则将当前物品整个装进背包
+            res += item.v;
+            cap -= item.w;
+        } else {
+            // 若剩余容量不足，则将当前物品的一部分装进背包
+            res += (item.v / item.w) * cap;
+            // 已无剩余容量，因此跳出循环
+            break;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const wgt = [10, 20, 30, 40, 50];
+const val = [50, 120, 150, 210, 240];
+const cap = 50;
+const n = wgt.length;
+
+// 贪心算法
+const res = fractional_knapsack(wgt, val, cap);
+console.log(`不超过背包容量的最大物品价值为 ${res}`);
diff --git a/codes/javascript/chapter_greedy/max_capacity.js b/codes/javascript/chapter_greedy/max_capacity.js
new file mode 100644
index 000000000..07858f3d0
--- /dev/null
+++ b/codes/javascript/chapter_greedy/max_capacity.js
@@ -0,0 +1,33 @@
+/**
+ * File: max_capacity.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 最大容量：贪心 */
+function max_capacity(ht) {
+    // 初始化 i, j 分列数组两端
+    let i = 0, j = ht.length - 1;
+    // 初始最大容量为 0
+    let res = 0;
+    // 循环贪心选择，直至两板相遇
+    while (i < j) {
+        // 更新最大容量
+        const cap = Math.min(ht[i], ht[j]) * (j - i);
+        res = Math.max(res, cap);
+        // 向内移动短板
+        if (ht[i] < ht[j]) {
+            i += 1;
+        } else {
+            j -= 1;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const ht = [3, 8, 5, 2, 7, 7, 3, 4];
+
+// 贪心算法
+const res = max_capacity(ht);
+console.log(`最大容量为 ${res}`);
diff --git a/codes/javascript/chapter_greedy/max_product_cutting.js b/codes/javascript/chapter_greedy/max_product_cutting.js
new file mode 100644
index 000000000..e2c6bf6e2
--- /dev/null
+++ b/codes/javascript/chapter_greedy/max_product_cutting.js
@@ -0,0 +1,33 @@
+/**
+ * File: max_product_cutting.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 最大切分乘积：贪心 */
+function max_product_cutting(n) {
+    // 当 n <= 3 时，必须切分出一个 1
+    if (n <= 3) {
+        return 1 * (n - 1);
+    }
+    // 贪心地切分出 3 ，a 为 3 的个数，b 为余数
+    let a = Math.floor(n / 3);
+    let b = n % 3;
+    if (b === 1) {
+        // 当余数为 1 时，将一对 1 * 3 转化为 2 * 2
+        return Math.pow(3, a - 1) * 2 * 2;
+    }
+    if (b === 2) {
+        // 当余数为 2 时，不做处理
+        return Math.pow(3, a) * 2;
+    }
+    // 当余数为 0 时，不做处理
+    return Math.pow(3, a);
+}
+
+/* Driver Code */
+let n = 58;
+
+// 贪心算法
+let res = max_product_cutting(n);
+console.log(`最大切分乘积为 ${res}`);
diff --git a/codes/typescript/chapter_greedy/coin_change_greedy.ts b/codes/typescript/chapter_greedy/coin_change_greedy.ts
new file mode 100644
index 000000000..678aaa21f
--- /dev/null
+++ b/codes/typescript/chapter_greedy/coin_change_greedy.ts
@@ -0,0 +1,50 @@
+/**
+ * File: coin_change_greedy.ts
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 零钱兑换：贪心 */
+function coin_change_greedy(coins: number[], amt: number): number {
+    // 假设 coins 数组有序
+    let i = coins.length - 1;
+    let count = 0;
+    // 循环进行贪心选择，直到无剩余金额
+    while (amt > 0) {
+        // 找到小于且最接近剩余金额的硬币
+        while (i > 0 && coins[i] > amt) {
+            i--;
+        }
+        // 选择 coins[i]
+        amt -= coins[i];
+        count++;
+    }
+    // 若未找到可行方案，则返回 -1
+    return amt === 0 ? count : -1;
+}
+
+/* Driver Code */
+// 贪心：能够保证找到全局最优解
+let coins: number[] = [1, 5, 10, 20, 50, 100];
+let amt: number = 186;
+let res: number = coin_change_greedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`凑到 ${amt} 所需的最少硬币数量为 ${res}`);
+
+// 贪心：无法保证找到全局最优解
+coins = [1, 20, 50];
+amt = 60;
+res = coin_change_greedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`凑到 ${amt} 所需的最少硬币数量为 ${res}`);
+console.log("实际上需要的最少数量为 3 ，即 20 + 20 + 20");
+
+// 贪心：无法保证找到全局最优解
+coins = [1, 49, 50];
+amt = 98;
+res = coin_change_greedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`凑到 ${amt} 所需的最少硬币数量为 ${res}`);
+console.log("实际上需要的最少数量为 2 ，即 49 + 49");
+
+export { };
diff --git a/codes/typescript/chapter_greedy/fractional_knapsack.ts b/codes/typescript/chapter_greedy/fractional_knapsack.ts
new file mode 100644
index 000000000..dfcf26ae9
--- /dev/null
+++ b/codes/typescript/chapter_greedy/fractional_knapsack.ts
@@ -0,0 +1,50 @@
+/**
+ * File: fractional_knapsack.ts
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 物品 */
+class Item {
+    w: number; // 物品重量
+    v: number; // 物品价值
+
+    constructor(w: number, v: number) {
+        this.w = w;
+        this.v = v;
+    }
+}
+
+/* 分数背包：贪心 */
+function fractional_knapsack(wgt: number[], val: number[], cap: number): number {
+    // 创建物品列表，包含两个属性：重量、价值
+    const items: Item[] = wgt.map((w, i) => new Item(w, val[i]));
+    // 按照单位价值 item.v / item.w 从高到低进行排序
+    items.sort((a, b) => (b.v / b.w) - (a.v / a.w));
+    // 循环贪心选择
+    let res = 0;
+    for (const item of items) {
+        if (item.w <= cap) {
+            // 若剩余容量充足，则将当前物品整个装进背包
+            res += item.v;
+            cap -= item.w;
+        } else {
+            // 若剩余容量不足，则将当前物品的一部分装进背包
+            res += (item.v / item.w) * cap;
+            // 已无剩余容量，因此跳出循环
+            break;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const wgt: number[] = [10, 20, 30, 40, 50];
+const val: number[] = [50, 120, 150, 210, 240];
+const cap: number = 50;
+
+// 贪心算法
+const res: number = fractional_knapsack(wgt, val, cap);
+console.log(`不超过背包容量的最大物品价值为 ${res}`);
+
+export { };
diff --git a/codes/typescript/chapter_greedy/max_capacity.ts b/codes/typescript/chapter_greedy/max_capacity.ts
new file mode 100644
index 000000000..2f8d99bea
--- /dev/null
+++ b/codes/typescript/chapter_greedy/max_capacity.ts
@@ -0,0 +1,35 @@
+/**
+ * File: max_capacity.ts
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 最大容量：贪心 */
+function max_capacity(ht: number[]): number {
+    // 初始化 i, j 分列数组两端
+    let i = 0, j = ht.length - 1;
+    // 初始最大容量为 0
+    let res = 0;
+    // 循环贪心选择，直至两板相遇
+    while (i < j) {
+        // 更新最大容量
+        const cap: number = Math.min(ht[i], ht[j]) * (j - i);
+        res = Math.max(res, cap);
+        // 向内移动短板
+        if (ht[i] < ht[j]) {
+            i += 1;
+        } else {
+            j -= 1;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const ht: number[] = [3, 8, 5, 2, 7, 7, 3, 4];
+
+// 贪心算法
+const res: number = max_capacity(ht);
+console.log(`最大容量为 ${res}`);
+
+export { };
diff --git a/codes/typescript/chapter_greedy/max_product_cutting.ts b/codes/typescript/chapter_greedy/max_product_cutting.ts
new file mode 100644
index 000000000..2d21c5318
--- /dev/null
+++ b/codes/typescript/chapter_greedy/max_product_cutting.ts
@@ -0,0 +1,35 @@
+/**
+ * File: max_product_cutting.ts
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* 最大切分乘积：贪心 */
+function max_product_cutting(n: number): number {
+    // 当 n <= 3 时，必须切分出一个 1
+    if (n <= 3) {
+        return 1 * (n - 1);
+    }
+    // 贪心地切分出 3 ，a 为 3 的个数，b 为余数
+    let a: number = Math.floor(n / 3);
+    let b: number = n % 3;
+    if (b === 1) {
+        // 当余数为 1 时，将一对 1 * 3 转化为 2 * 2
+        return Math.pow(3, a - 1) * 2 * 2;
+    }
+    if (b === 2) {
+        // 当余数为 2 时，不做处理
+        return Math.pow(3, a) * 2;
+    }
+    // 当余数为 0 时，不做处理
+    return Math.pow(3, a);
+}
+
+/* Driver Code */
+let n: number = 58;
+
+// 贪心算法
+let res: number = max_product_cutting(n);
+console.log(`最大切分乘积为 ${res}`);
+
+export { };