518.零钱兑换-ii ​

/**
 * @param {number} amount
 * @param {number[]} coins
 * @return {number}
 */
var change = function (amount, coins) {
  const dp = new Array(amount + 1).fill(0);
  dp[0] = 1;

  for (let i = 0; i < coins.length; i++) {
    // 完全背包问题 正序
    for (let j = coins[i]; j <= amount; j++) {
      dp[j] += dp[j - coins[i]];
    }
  }
  return dp[amount];
};

/**
 * @param {number} amount
 * @param {number[]} coins
 * @return {number}
 */
var change = function (amount, coins) {
  const dp = new Array(amount + 1).fill(0);
  dp[0] = 1;

  for (let i = 0; i < coins.length; i++) {
    // 完全背包问题 正序
    for (let j = coins[i]; j <= amount; j++) {
      dp[j] += dp[j - coins[i]];
    }
  }
  return dp[amount];
};