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描述
You are given an integer array nums (0-indexed). In one operation, you can choose an element of the array and increment it by 1.
- For example, if nums = [1,2,3], you can choose to increment nums[1] to make nums = [1,3,3].
- Return the minimum number of operations needed to make nums strictly increasing.
An array nums is strictly increasing if nums[i] < nums[i+1] for all 0 <= i < nums.length - 1. An array of length 1 is trivially strictly increasing.
Example 1:
Input: nums = [1,1,1]
Output: 3
Explanation: You can do the following operations:
1) Increment nums[2], so nums becomes [1,1,2].
2) Increment nums[1], so nums becomes [1,2,2].
3) Increment nums[2], so nums becomes [1,2,3].
Example 2:
Input: nums = [1,5,2,4,1]
Output: 14
Example 3:
Input: nums = [8]
Output: 0
Note:
1 <= nums.length <= 5000
1 <= nums[i] <= 10^4
解析
根据题意，就是将 nums 经过特定操作转换为增序列，特定操作就是能够每次对某一个元素加一，求最后将 nums 转换为增序列至少需要多少次操作。很简单就是遍历所有元素，如果后一个元素小于等于前一个元素，那么将后一个元素变为前一个元素加一的大小即可，将操作次数加入 result ，遍历结束得到的 result 即为结果。
解答
class Solution(object):
def minOperations(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
result = 0
i = 1
while i < len(nums):
if nums[i] <= nums[i-1]:
increment = nums[i - 1] - nums[i] + 1
result += increment
nums[i] += increment
i += 1
return result
运行结果
Runtime: 108 ms, faster than 39.07% of Python online submissions for Minimum Operations to Make the Array Increasing.
Memory Usage: 14.1 MB, less than 20.09% of Python online submissions for Minimum Operations to Make the Array Increasing.
解析
思路还和上面一样的，其实还可以更加地简化一下代码过程，遍历 nums 中的每个元素，如果当前元素大于 p 直接使用 p 记录，否则将 p 增加 1 表示当前位置应该存在的最小的数字，然后用 result 来记录当前元素 增加到应该存在的最小的数字需要操作的次数，最后遍历结束得到的 result 就是结果。
解答
class Solution(object):
def minOperations(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
p,result=0,0
for num in nums:
if p < num:
p = num
else:
p += 1
result += p - num
return result
运行结果
Runtime: 92 ms, faster than 94.77% of Python online submissions for Minimum Operations to Make the Array Increasing.
Memory Usage: 13.8 MB, less than 99.35% of Python online submissions for Minimum Operations to Make the Array Increasing.
原题链接：leetcode.com/problems/mi…
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