SQL - UNION

union all
Merge all column with same no. of column (Diff type would be OK but may loss some data) 

union
Like union all but will remove duplicated rows like distinct










 

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MAP - Sort with stream

 LEETCODE 1636 Given an array of integers   nums , sort the array in   increasing   order based on the frequency of the values. If multiple values have the same frequency, sort them in   decreasing   order. Return the  sorted array . Example 1: Input: nums = [1,1,2,2,2,3] Output: [3,1,1,2,2,2] Explanation: '3' has a frequency of 1, '1' has a frequency of 2, and '2' has a frequency of 3. Example 2: Input: nums = [2,3,1,3,2] Output: [1,3,3,2,2] Explanation: '2' and '3' both have a frequency of 2, so they are sorted in decreasing order. Example 3: Input: nums = [-1,1,-6,4,5,-6,1,4,1] Output: [5,-1,4,4,-6,-6,1,1,1] #1 class Solution { public int[] frequencySort(int[] nums) { return Arrays.stream(nums) .boxed() // boxing to wapped class .collect(Collectors.toMap(e-> e , e-> 1 , Integer::sum))//?? .entrySet() .stream() .sorted((e1,e2) -> e1.getValue().equals(e...
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JAVA - DSF Example

  class Solution { class Point { int x ; int y ; int steps ; public Point ( int x , int y , int steps ){ this . x = x; this . y = y; this . steps = steps; } } public int shortestPathBinaryMatrix ( int [][] grid ) { //BFS //DFS //BFS -> Shortest path //DSA : Queue if (grid[ 0 ][ 0 ] != 0 ){ return - 1 ; } int [][] moves = new int [][]{{ 0 ,- 1 } , { 0 , 1 } , { 1 , 0 }, {- 1 , 0 } , {- 1 ,- 1 },{- 1 , 1 },{ 1 , 1 },{ 1 ,- 1 }}; Stack < Point > queue = new Stack <>(); queue . push ( new Point ( 0 , 0 , 1 )); grid[ 0 ][ 0 ] = 1 ; int newX = 0 ; int newY = 0 ; while (! queue . isEmpty ()){ Point point = queue . pop (); if ( point . x == grid . length - 1 && point . y == grid[ 0 ]. length - 1 ){ ...
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