1570. Final Prices With a Special Discount in a Shop

难度: Easy

题目描述

You are given an integer array prices where prices[i] is the price of the ith item in a shop.

There is a special discount for items in the shop. If you buy the ith item, then you will receive a discount equivalent to prices[j] where j is the minimum index such that j > i and prices[j] <= prices[i]. Otherwise, you will not receive any discount at all.

Return an integer array answer where answer[i] is the final price you will pay for the ith item of the shop, considering the special discount.

 

Example 1:

Input: prices = [8,4,6,2,3]
Output: [4,2,4,2,3]
Explanation: 
For item 0 with price[0]=8 you will receive a discount equivalent to prices[1]=4, therefore, the final price you will pay is 8 - 4 = 4.
For item 1 with price[1]=4 you will receive a discount equivalent to prices[3]=2, therefore, the final price you will pay is 4 - 2 = 2.
For item 2 with price[2]=6 you will receive a discount equivalent to prices[3]=2, therefore, the final price you will pay is 6 - 2 = 4.
For items 3 and 4 you will not receive any discount at all.

Example 2:

Input: prices = [1,2,3,4,5]
Output: [1,2,3,4,5]
Explanation: In this case, for all items, you will not receive any discount at all.

Example 3:

Input: prices = [10,1,1,6]
Output: [9,0,1,6]

 

Constraints:

• 1 <= prices.length <= 500
• 1 <= prices[i] <= 1000

解题思路

代码实现

解决方案

java

class Solution {
    public int[] finalPrices(int[] prices) {
        int n = prices.length;
        int[] ans = new int[n];
        Deque<Integer> stack = new ArrayDeque<Integer>();
        for (int i = n - 1; i >= 0; i--) {
            while (!stack.isEmpty() && stack.peek() > prices[i]) {
                stack.pop();
            }
            ans[i] = stack.isEmpty() ? prices[i] : prices[i] - stack.peek();
            stack.push(prices[i]);
        }
        return ans;
    }
}