"Leetcode Problem Solving report" array element delete

Leetcode Remove Element

Problem description

Given an array and a value, remove all instances of that value in place and return the new length. Do the allocate extra space for another array, and you must does this on place with constant memory. The order of elements can be changed. It doesn ' t matter what are you leave beyond the new length.

For example, given input array nums = [3,2,2,3] , val = 3. Your function should return length = 2, with the first of the elements of Nums being 2.

Analysis and Solution

Note: The order of elements can be changed, it is possible to find a position equal to Val from scratch, a position that is not equal to Val at the beginning of the tail, and an interchange with a double pointer, until the head and tail pointers cross. The reference code looks like this:

1 classSolution2 {3  Public:4     intRemoveelement (vector<int>& Nums,intval)5     {6         intLen = Nums.size (), i =0, j = Len-1; 7         if(J <0)return 0; 8          while(I <j)9         {Ten              while(I < len && nums[i]! = val) i++;  One              while(J >=0&& Nums[j] = = val) j--;  A             if(I < J) Swap (nums[i++], nums[j--]);  -         } -         return(Nums[j] = = val)? j:j+1;  the     } -};

View Code leetcode Remove duplicates from Sorted Array

Problem description

Given a sorted array, remove the duplicates in place such, all element appear only once and return the new L Ength. Do the allocate extra space for another array, and you must does this on place with constant memory.

For example, given input array nums = We [1,1,2]. Y function should return length = 2 , with the first Elements of nums being and 1 2 respectively. It doesn ' t matter what are you leave beyond the new length.

Analysis and Solution

Go to the weight, the reference code is as follows:

1 classSolution2 {3  Public:4     intRemoveDuplicates (vector<int>&nums)5     {6         intRET =0, length =nums.size ();7         if(Length <2)returnlength;8          for(inti =1; i < length; i++)9         {Ten             if(Nums[i]! = Nums[ret]) Nums[++ret] =Nums[i]; One         } A         returnret+1;  -     } -};

View Code leetcode Remove duplicates from Sorted Array II

Problem description

follow up for "Remove duplicates": What if duplicates is allowed at the most twice?

For example, Given sorted array nums = [1,1,1,2,2,3].  Your function should return length =5, with the first five elements ofNumsbeing1, 1, 2, 2 and3. It doesn ' t matter what are you leave beyond the new length.

Analysis and Solution

Go heavy, but note that the same value in the result can occur two times, the last problem extension, in fact, can be extended to the same value occurs k times. The reference code is as follows:

1 classSolution2 {3  Public:4     intRemoveDuplicates (vector<int>&nums)5     {6         intLen = Nums.size (), i =1, j =2; 7         if(Len <3)returnLen;8          while(J <len)9         {Ten             if(Nums[j]! = nums[i-1]) Nums[++i] =Nums[j]; OneJ + +;  A         } -         returni +1;  -     } the};

View Code leetcode 283 Move Zeros

Problem description

　　Given an array nums , write a function to move all's to the 0 end of it while maintaining the relative order of the No N-zero elements.

For example, given nums = [0, 1, 0, 3, 12] , after calling your function, nums should is [1, 3, 12, 0, 0] .

Note:

1. You must does this in-place without making a copy of the array.

2. Minimize the total number of operations.

Analysis and Solution

Note that elements other than 0 are kept in the original order, still double pointers, but this is all starting from the beginning, I point to the first 0,j to the first non-0, the interchange, until the end of the array is J. The reference code looks like this:

1 classSolution2 {3  Public:4     voidMovezeroes (vector<int>&nums)5     {6         intLen = Nums.size (), i =0, j =0; 7          while(I <len)8         {9             if(Nums[i]! =0) Swap (nums[j++], nums[i]); Teni++;  One         } A     } -};

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"Leetcode Problem Solving report" array element delete