Leetcode: 1449. Form Largest Integer With Digits That Add up to Target

Description

Given an array of integers cost and an integer target. Return the maximum integer you can paint under the following rules:

The cost of painting a digit (i+1) is given by cost[i] (0 indexed).
The total cost used must be equal to target.
Integer does not have digits 0.
Since the answer may be too large, return it as string.

If there is no way to paint any integer given the condition, return "0".

Example

Input: cost = [6,10,15,40,40,40,40,40,40], target = 47
Output: "32211"

Note

cost.length == 9
1 <= cost[i] <= 5000
1 <= target <= 5000

分析

code

第一次提交就 AC 的代码， 
Runtime: 292 ms, faster than 60.00% of Python online submissions for Form Largest Integer With Digits That Add up to Target.
Memory Usage: 25.1 MB, less than 39.85% of Python online submissions for Form Largest Integer With Digits That Add up to Target.

class Solution(object):
    def largestNumber(self, costs, target):
        """
        :type cost: List[int]
        :type target: int
        :rtype: str
        """
        
        def mmax(a, b):
            if len(a) > len(b):
                return a
            elif len(b) > len(a):
                return b
            return max(a, b)

        helper = {}
        for i, v in enumerate(costs):
            helper[v] = str(i+1)

        dp = ['0' for _ in range(target+1)]

        for k in helper:
            try:
                dp[k] = helper[k]
            except:
                continue

        r = []
        for i in range (2, min(10, target+1)):
            for j in helper:
                if j >= i or dp[i-j] == '0':
                    continue
                r.append(i)
                dp[i] = mmax(dp[i], max(dp[i-j], dp[j]) + min(dp[i-j], dp[j]))

        for i in r:
            helper.pop(i, 0)

        for i in range(10, target+1):
            for j in helper:
                if j >= i or dp[i-j] == '0':
                    continue
                dp[i] = mmax(dp[i], max(dp[j]+dp[i-j], dp[i-j]+dp[j]))
        return dp[-1]

总结

• 比较简单的 dp ，不应该归类为 hard 级别的 dp