Feat : Coin-Change

dynamic_programming/coin_change.ts

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+/**
+ * Calculates the number of ways to make a target amount using given coin denominations.
+ *
+ * @param coins - An array of coin denominations.
+ * @param numberOfWays - The number of ways to represent the target amount using the given coins.
+ * @param targetAmount - The target sum to achieve.
+ * @returns The number of ways to make the target amount with the given coins.
+ */
+export function coinChange(coins: number[], numberOfWays: number, targetAmount: number): number {
+
+    const dp: number[] = new Array(targetAmount + 1).fill(0);
+    dp[0] = 1;
+
+    for (let coinIndex = 0; coinIndex < numberOfWays; coinIndex++) {
+        const coinValue = coins[coinIndex];
+        for (let currentAmount = coinValue; currentAmount <= targetAmount; currentAmount++) {
+            dp[currentAmount] += dp[currentAmount - coinValue];
+        }
+    }
+
+    return dp[targetAmount];
+}

dynamic_programming/test/coin_change.test.ts

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+import { coinChange } from "../coin_change";
+
+describe('Coin Change problem ', () => {
+    it('should return 0 if there are no coins', () => {
+        const coins: number[] = [];
+        const numCoins: number = coins.length;
+        const targetAmount: number = 5;
+        const ways = coinChange(coins, numCoins, targetAmount);
+        expect(ways).toBe(0);
+    });
+
+    it('should return 1 when the target amount is 0', () => {
+        const coins: number[] = [1, 2, 3];
+        const numCoins: number = coins.length;
+        const targetAmount: number = 0;
+        const ways = coinChange(coins, numCoins, targetAmount);
+        expect(ways).toBe(1);
+    });
+
+    it('should calculate the number of ways correctly', () => {
+        const coins: number[] = [1, 2, 3];
+        const numCoins: number = coins.length;
+        const targetAmount: number = 5;
+        const ways = coinChange(coins, numCoins, targetAmount);
+        expect(ways).toBe(5);
+    });
+
+    it('should handle a large target amount', () => {
+        const coins: number[] = [1, 2, 3];
+        const numCoins: number = coins.length;
+        const targetAmount: number = 1000;
+        const ways = coinChange(coins, numCoins, targetAmount);
+        expect(ways).toBeGreaterThan(0);
+    });
+
+    it('should handle a large number of coin denominations', () => {
+        const coins: number[] = new Array(100).fill(1);
+        const numCoins: number = coins.length;
+        const targetAmount: number = 5;
+        const ways = coinChange(coins, numCoins, targetAmount);
+        expect(ways).toBeGreaterThan(0);
+    });
+});