download：拉勾-算法突击特训营3期【完整无密】
leetcode 2295. Replace Elements in an Array
描绘
You are given a 0-indexed array nums that consists of n distinct positive integers. Apply m operations to this array, where in the ith operation you replace the number operations[i][0] with operations[i][1].
It is guaranteed that in the ith operation:
operations[i][0] exists in nums.
operations[i][1] does not exist in nums.
Return the array obtained after applying all the operations.
Example 1:
Input: nums = [1,2,4,6], operations = [[1,3],[4,7],[6,1]]
Output: [3,2,7,1]
Explanation: We perform the following operations on nums:
- Replace the number 1 with 3. nums becomes [3,2,4,6].
- Replace the number 4 with 7. nums becomes [3,2,7,6].
- Replace the number 6 with 1. nums becomes [3,2,7,1].
We return the final array [3,2,7,1].
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Example 2:
Input: nums = [1,2], operations = [[1,3],[2,1],[3,2]]
Output: [2,1]
Explanation: We perform the following operations to nums:
- Replace the number 1 with 3. nums becomes [3,2].
- Replace the number 2 with 1. nums becomes [3,1].
- Replace the number 3 with 2. nums becomes [2,1].
We return the array [2,1].
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Note:
n == nums.length
m == operations.length
1 <= n, m <= 10^5
All the values of nums are distinct.
operations[i].length == 2
1 <= nums[i], operations[i][0], operations[i][1] <= 10^6
operations[i][0] will exist in nums when applying the ith operation.
operations[i][1] will not exist in nums when applying the ith operation.
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解析
依据题意，给定一个由 n 个不同的正整数组成的索引为 0 的数组 nums 。 对这个数组应用 m 个操作，在第 i 个操作中，将数字 operations[i][0] 交换为 operations[i][1] 。
标题保证在第 i 次操作中：
operation[i][0] 存在于 nums 中
operation[i][1] 在 nums 中不存在
返回应用一切操作后得到的数组。
这道题其实依照题意就能够了，需求留意的中央是我们要运用字典 d 来保管每个元素的索引，并且在停止操作之后将每个字符对应的索引停止更新即可。
时间复杂度为 O(N) ，空间复杂度为 O(N) 。
解答
class Solution(object):
def arrayChange(self, nums, operations):
"""
:type nums: List[int]
:type operations: List[List[int]]
:rtype: List[int]
"""
N = len(operations)
d = {}
for i, c in enumerate(nums):
d[c] = i
for i in range(N):
x, y = operations[i]
idx = d[x]
nums[idx] = y
d[y] = idx
return nums
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运转结果
80 / 80 test cases passed.
Status: Accepted
Runtime: 1826 ms
Memory Usage: 73.6 MB
