new graduate转MLE打卡

研究生12月就毕业啦，学的东西很杂，之前刷题都集中在绿皮书上，面试的时候被问到leetcode的题没答上有点难受，所以我准备刷题转machine learning engineer。

打卡打卡。

Leetcode 75 Sort Colors.  思路：设置 三个pointer，遇到和中间pointer一样的element，pointer加一，如果element比较大，那么交换pointer所指的element（white 和blue），大的pointer 减一。如果element比较小，交换pointer所指的element（red和white），然后两个pointer都加一。

Leetcode 79 Word Search。 思路：DFS，iterate the matrix，for every element which corresponds to the word, find its neighboring element to check they are the same as the next letter in the word and run dfs again, notice that when run dfs again, assign a rare letter to previous element since the element shouldn't be used more than once.(in solution, they use '#'. eg: temp = board[i][j], board[i][j] = '#', after dfs, board[i][j] = temp)

Leetcode 74 Search a 2-D matrix. idea: binary search. Notice that the middle point in a matrix is matrix[mid/cols][mid%cols] where mid = (rows * cols )/ 2

楼主写这些思路只是为了自己加深记忆，详细答案和思路还请去leetcode官网详查。

Leetcode 88 Merge Sorted Array.  Compare two last elements in the list and put what is larger on the last position of nums1, next is m = m -1(or n = n-1). if there are some elements in nums2 left, we set nums1[:n] = nums2[:n]

Leetcode 80. Remove Duplicates from Sorted Array II. set a variable called i , if i <2 or  n > nums[i]-2: nums[i] = n ,  i = i +1

周末好忙，总是在写作业。。。

论坛用不熟练 东西没发出来。昨天做了62，63，64.都是用DP 看了答案之后觉得题不难，比较好写。 还做了73题，是个最优化空间复杂度的题，要掌握基本解法和空间最优解，用最优解的时候（set the first element in that row and column to zero respectively ），要记住顺序，不然会记重。我给朋友说了这个题他说没意思hhhh

今天回顾了Leetcode: 11.Container With Most Water  (Two pointer)  。在discussion里面看到一个简单的方法，while(left< right):  之后判断height[left]和height[right]大小，然后直接求max_area。不能只记住思想，还要记住为啥这样可以，

Leetcode 78. Subsets. DFS,

Leetcode 152. Maximum Product Subarray DP

Leetcode 120. Triangle DP

Leetcode 162. Find Peak Element : binary search. note that mid = l + (r-l)//2

Leetcode 167. Two Sum II: binary search or two pointer. two pointer method would be better in terms of time efficiency.

Leetcode 169. Majority Element.  dictionary or use two variable to keep track of the most frequent element.

Leetcode 153 : binary search

Leetcode 189: Rotate Array 三次reverse
Leetcode 209: Minimum Size Subarray Sum. Sliding window?

Leetcode ：217 ，219 ，287

start with tag'string' today. I have finished
Leetcode 3.
Leetcode 14.