描述
Given an array target and an integer n. In each iteration, you will read a number from list = {1,2,3..., n}.
Build the target array using the following operations:
- Push: Read a new element from the beginning list, and push it in the array.
- Pop: delete the last element of the array.
- If the target array is already built, stop reading more elements.
Return the operations to build the target array. You are guaranteed that the answer is unique.
Example 1:
Input: target = [1,3], n = 3
Output: ["Push","Push","Pop","Push"]
Explanation:
Read number 1 and automatically push in the array -> [1]
Read number 2 and automatically push in the array then Pop it -> [1]
Read number 3 and automatically push in the array -> [1,3]
Example 2:
Input: target = [1,2,3], n = 3
Output: ["Push","Push","Push"]
Example 3:
Input: target = [1,2], n = 4
Output: ["Push","Push"]
Explanation: You only need to read the first 2 numbers and stop.
Example 4:
Input: target = [2,3,4], n = 4
Output: ["Push","Pop","Push","Push","Push"]
Note:
- 1 <= target.length <= 100
- 1 <= target[i] <= n
- 1 <= n <= 100
- target is strictly increasing.
解析
根据题意，因为 target 是升序的，所以只要遍历 [1,target[-1]+1] 的所有元素，只要每个元素在 target 中存在，就在 res 中添加 Push，如果不存在就添加 Push 和 Pop ，遍历结束得到的就是答案。
解答
class Solution(object):
def buildArray(self, target, n):
"""
:type target: List[int]
:type n: int
:rtype: List[str]
"""
ans = []
for i in range(1,target[-1]+1):
if i in target:
ans.append("Push")
else:
ans.append("Push")
ans.append("Pop")
return ans
运行结果
Runtime: 20 ms, faster than 69.23% of Python online submissions for Build an Array With Stack Operations.
Memory Usage: 13.2 MB, less than 93.27% of Python online submissions for Build an Array With Stack Operations.
原题链接：leetcode.com/problems/bu…
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