Add coin-change solution

Author: Jeehay28

coin-change/Jeehay28.js

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+/**
+ * @param {number[]} coins
+ * @param {number} amount
+ * @return {number}
+ */
+
+// TC : O(c*a), where c is the number of coins, and a is amount
+// SC : O(a) // dp array requires O(a) space
+
+var coinChange = function (coins, amount) {
+  // dynamic programming approach
+
+  // dp[amount] : the minimum number of coins
+  // as a default, dp[0] = 0, for other amounts, dp[amount] = amount + 1 ()
+  // [0, amount+1, amount+1, ...]
+  const dp = [0, ...new Array(amount).fill(amount + 1)];
+
+  // start from coin because i - coin >= 0
+  for (const coin of coins) {
+    for (let i = coin; i <= amount; i++) {
+      // dp[i] : not using the current coin
+      // dp[i - coin] + 1 : using the current coin
+      dp[i] = Math.min(dp[i - coin] + 1, dp[i]);
+    }
+  }
+
+  // dp[amount] === amount + 1 : that amount of money cannot be made up by any combination of the coins
+  return dp[amount] < amount + 1 ? dp[amount] : -1;
+};
+
+