maximum-value-of-k-coins-from-piles

array/maximum-value-of-k-coins-from-piles.js

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+/**
+2218. Maximum Value of K Coins From Piles
+
+There are n piles of coins on a table. Each pile consists of a positive number of coins of assorted denominations.
+
+In one move, you can choose any coin on top of any pile, remove it, and add it to your wallet.
+
+Given a list piles, where piles[i] is a list of integers denoting the composition of the ith pile from top to bottom, and a positive integer k, return the maximum total value of coins you can have in your wallet if you choose exactly k coins optimally.
+
+Example 1:
+Input: piles = [[1,100,3],[7,8,9]], k = 2
+Output: 101
+Explanation:
+The above diagram shows the different ways we can choose k coins.
+The maximum total we can obtain is 101.
+
+Example 2:
+Input: piles = [[100],[100],[100],[100],[100],[100],[1,1,1,1,1,1,700]], k = 7
+Output: 706
+Explanation:
+The maximum total can be obtained if we choose all coins from the last pile.
+
+Constraints:
+n == piles.length
+1 <= n <= 1000
+1 <= piles[i][j] <= 105
+1 <= k <= sum(piles[i].length) <= 2000
+*/
+
+/**
+ * @param {number[][]} piles
+ * @param {number} k
+ * @return {number}
+ */
+var maxValueOfCoins = function (piles, k) {
+  const n = piles.length;
+  const cache = {};
+
+  const getMaxValue = (i, k) => {
+    if (i >= n || k <= 0) {
+      return 0;
+    }
+
+    const key = i + "," + k;
+
+    if (cache[key]) {
+      return cache[key];
+    }
+
+    let result = getMaxValue(i + 1, k);
+
+    let sum = 0;
+
+    for (let j = 0; j < piles[i].length && j < k; j++) {
+      sum += piles[i][j];
+
+      result = Math.max(result, sum + getMaxValue(i + 1, k - j - 1));
+    }
+
+    return (cache[key] = result);
+  };
+
+  return getMaxValue(0, k);
+};

string/palindrome-number.js

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+/**
+9. Palindrome Number
+
+Given an integer x, return true if x is a 
+palindrome, and false otherwise.
+
+Example 1:
+Input: x = 121
+Output: true
+Explanation: 121 reads as 121 from left to right and from right to left.
+
+Example 2:
+Input: x = -121
+Output: false
+Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
+
+Example 3:
+Input: x = 10
+Output: false
+Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
+
+Constraints:
+-231 <= x <= 231 - 1
+
+Follow up: Could you solve it without converting the integer to a string?
+*/
+
+/**
+ * @param {number} x
+ * @return {boolean}
+ */
+var isPalindrome = function (x) {
+  const str = `${x}`;
+  let left = 0;
+  let right = str.length - 1;
+
+  while (left < right) {
+    if (str[left] !== str[right]) {
+      return false;
+    }
+
+    left++;
+    right--;
+  }
+
+  return true;
+};