• Binary Search (Tree) & Binary Reduction
• Sorting Algorithm

This page is used to record the problems that I have been solved, and they are classified by types.

The answers are all the most understandable and the time and space complexity can be accepted in the interview.

Binary Search (Tree) & Binary Reduction

Easy

278. First Bad Version        Solution

374. Guess Number Higher or Lower        Solution

35. Search Insert Position        Solution

367. Valid Perfect Square         Solution

Note of 69

        Binary search problem should be pay attention that the value in the loop may overflow, so 69 and 367 should use long.

69. Sqrt(x)        Solution

367. Valid Perfect Square        Solution

700. Search in a Binary Search Tree        Solution

Medium

34. Find First and Last Position of Element in Sorted Array        Solution

162. Find Peak Element        Solution

74. Search a 2D Matrix        Solution

240. Search a 2D Matrix II        Solution

Note of 33

         33, 81, 153, 154 can be solved in the same idea. 154 is a hard problem, but it is the pre-problem of 81.
         If the elements are not necessarily with distinct values, every binary search loop should be pay attention to nums[mid] == nums[last]. When this situation happens, we can only drop one element(last) from the nums, because we do not know if the target is in the left part or in the right part.

33. Search in Rotated Sorted Array        Solution

81. Search in Rotated Sorted Array II        Solution

153. Find Minimum in Rotated Sorted Array        Solution

Note of 1011

         1011, 410(hard), 1482, 1891 can be solved in the same idea. Try to find the possible result area, and then use the binary search to find the right result.

1011. Capacity To Ship Packages Within D Days         Solution

1482. Minimum Number of Days to Make m Bouquets        Solution

1891. Cutting Ribbons        Solution

658. Find K Closest Elements        Solution

702. Search in a Sorted Array of Unknown Size        Solution

Hard

154. Find Minimum in Rotated Sorted Array II        Solution

410. Split Array Largest Sum        Solution

Sorting Algorithm

Easy

Note of 283

         283 and 75(medium) can be solved by setting multiple board, each board's left is the correct results, and in the loop we will not care about the board's right part.when the loop is over, we can make sure that the total result is right.

283. Move Zeroes        Solution

Medium

75. Sort Colors        Solution

692. Top K Frequent Words        Solution

Note of 912

         912 is the basic problem of sorting algorithm, we should know how to implement all of them: bubble, selection, insertion, quick, merge. The theories of them can be found easily.

912. Sort an Array        Solution

215. Kth Largest Element in an Array        Solution

451. Sort Characters By Frequency        Solution

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