[solutions][dp] Add solution to Coin Change in JS.

solutions/dp/coinChange.js

@@ -0,0 +1,91 @@
+/*
+TOP-DOWN DP SOLUTION
+*/
+const CANNOT_PRODUCE_SPECIFIED_AMOUNT = -1;
+
+const coinChangeHelper = (coins, amount, cache) => {
+  const amountInCache = cache.hasOwnProperty(amount);
+
+  if (amountInCache) {
+    return cache[amount];
+  }
+
+  let fewestCoinsToMakeAmount = Infinity;
+
+  coins.forEach((coinAmount) => {
+    const remainingAmount = amount - coinAmount;
+
+    if (remainingAmount < 0) return;
+
+    const remainingCoinsRequired = coinChangeHelper(
+      coins,
+      remainingAmount,
+      cache,
+    );
+
+    if (remainingCoinsRequired === CANNOT_PRODUCE_SPECIFIED_AMOUNT) return;
+
+    fewestCoinsToMakeAmount = Math.min(
+      fewestCoinsToMakeAmount,
+      1 + remainingCoinsRequired,
+    );
+  });
+
+  if (fewestCoinsToMakeAmount === Infinity) {
+    fewestCoinsToMakeAmount = CANNOT_PRODUCE_SPECIFIED_AMOUNT;
+  }
+
+  cache[amount] = fewestCoinsToMakeAmount;
+
+  return cache[amount];
+};
+
+const coinChange = (coins, amount) => {
+  const cache = {};
+
+  cache[0] = 0;
+
+  return coinChangeHelper(coins, amount, cache);
+};
+
+/*
+BOTTOM-UP DP SOLUTION
+*/
+const CANNOT_PRODUCE_SPECIFIED_AMOUNT = -1;
+
+const coinChange = (coins, targetAmount) => {
+  const cache = {};
+
+  cache[0] = 0;
+
+  for (let curAmount = 1; curAmount <= targetAmount; curAmount++) {
+    let fewestCoinsToMakeCurAmount = Infinity;
+
+    coins.forEach((coinAmount) => {
+      const remainingAmount = curAmount - coinAmount;
+
+      if (remainingAmount < 0) return;
+
+      // If `remainingAmount` is in `cache`, set `minCoinsToMakeRemainingAmount` to `cache[remainingAmount]. Otherwise, set it to `Infinity`.
+      const remainingAmountInCache = cache.hasOwnProperty(remainingAmount);
+      const minCoinsToMakeRemainingAmount = remainingAmountInCache
+        ? cache[remainingAmount]
+        : Infinity;
+
+      fewestCoinsToMakeCurAmount = Math.min(
+        fewestCoinsToMakeCurAmount,
+        1 + minCoinsToMakeRemainingAmount,
+      );
+    });
+
+    cache[curAmount] = fewestCoinsToMakeCurAmount;
+  }
+
+  const result = cache[targetAmount];
+
+  if (result === Infinity) {
+    return CANNOT_PRODUCE_SPECIFIED_AMOUNT;
+  }
+
+  return result;
+};