325. Maximum Size subarray Sum equals K and the oldest array equal to K

[Copy question]:

Given an array nums and a target value K, find the maximum length of a subarray that sums to K. If there isn ' t one, return 0 instead.

Note:
The sum of the entire nums array is guaranteed to fit within the 32-bit signed integer range.

Example 1:

Given nums = [1, -1, 5, -2, 3] , k = 3 ,
Return 4 . (Because the Subarray sums to 3 and is the [1, -1, 5, -2] longest)

Example 2:

Given nums = [-2, -1, 2, 1] , k = 1 ,
Return 2 . (Because the Subarray sums to 1 and is the [-1, 2] longest)

Follow up:
Can do it in O (n) time?

[Brute force solution]:

Time Analysis:

Spatial Analysis:

[After optimization]:

Time Analysis:

Spatial Analysis:

[Wonderful output CONDITIONS]:

[Wonderful corner case]:

[Thinking questions]:

Think only Max (Max, a) can take the longest, do not know how to write. In fact, the General idea of sum as I increases and grow longer, I give for once again on the line.

[a sentence of thought]:

Gap in a sudden increase in K, index also take the corresponding value can be

[input]: null: Normal: Large: Extra Small: Special cases handled in the program: abnormal conditions (unreasonable input):

[Drawing]:

[One brush]:

1. Map.containskey (sum) is useless and must be sum = = k .

[Two brushes]:

[Three brushes]:

[Four brushes]:

[Five brushes]:

[Results of five-minute visual debug]:

[Summary]:

Must consider the gapin the middle. Gap in a sudden increase in K, index also take the corresponding value can be

[Complexity]:time Complexity:o (n) Space complexity:o (n)

[English data structure or algorithm, why not other data structures or algorithms]:

To accumulate with a constant sum, the array cannot:

Sum[i] + = nums[i]; It's like every number has been re-added.

[Algorithmic thinking: Recursion/division/greed]:

[Key templating code]:

[Other solutions]:

[Follow up]:

[The problem given by the LC becomes variable]:

2 Sum:hashmap

[Code Style]:

classSolution { Public intMaxsubarraylen (int[] Nums,intk) {//cc        if(Nums = =NULL|| Nums.length = = 0)return0; //Ini:hashmap, MaxHashmap<integer, integer> map =NewHashmap<>(); intmax = 0, sum = 0; //For loop:3 conditions         for(inti = 0; i < nums.length; i++) {sum+=Nums[i]; //contains, Gap, not contains            if(sum = = k) Max = i + 1; Else if(Map.containskey (sum-k)) max = Math.max (max, i-map.get (Sum-k)); if(!map.containskey (sum)) map.put (sum, i); }                returnMax; }}

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325. Maximum Size subarray Sum equals K and the oldest array equal to K