Counting sort ............123

#1

code given on geeksforgeeks I don’t understand

#2

int max = Arrays.stream(arr).max().getAsInt();
int min = Arrays.stream(arr).min().getAsInt();
whats this?

#3

@Dhruv-Goyal-449223618988467
int max = Arrays.stream(arr).max().getAsInt();
int min = Arrays.stream(arr).min().getAsInt();
Arrays.stream(arr) is inbuilt function to get max and min without writing the iterative for loop to get max and min.

#4

ya clear till 2nd point, difficulty in 3rd point, pls used to send chatting link on emails.

#5

let array is 1,4,1,5,1,5
then what this int min = Arrays.stream(arr).min().getAsInt(); gives in ans
is it 1 or 0
and if consider neg integers what this gives,neg of taken array

#6

@Dhruv-Goyal-449223618988467
Arrays.stream(arr).min().getAsInt() will give 1 as an answer,as it is just shortcut to find minimum element in the Array.
Array: 1,4,1,5,1,5 is having 1 as its minimum.
Now for the negative part:
Consider an array of -1,0,-3,-2,10.
The Array is having -3 as minimum,hence Arrays.stream(arr).min().getAsInt() will give -3 as an answer in this array.

#7

As i saw algo on geeksforgeeks
Suppose array is 1,3,1,5,1,5
for(i=0,i<arr.len,i++)
Count[arr[i]-min]++.
Let i=5 ,arr[i]=5
But arr[i]-min=5-1=4 (bcoz min =1)
Count[4] get incremented to 1 from 0
But i want to increment arr[5] bcoz 5 occurs multiple times and 4 not occur a single time

#8

@Dhruv-Goyal-449223618988467
There are 4 major steps in this code:

int max = Arrays.stream(arr).max().getAsInt();
int min = Arrays.stream(arr).min().getAsInt();
int range = max - min + 1;
int count[] = new int[range];
int output[] = new int[arr.length];
for (int i = 0; i < arr.length; i++)
{
count[arr[i] - min]++;
}

    for (int i = 1; i < count.length; i++)  
    { 
        count[i] += count[i - 1]; 
    } 

    for (int i = arr.length - 1; i >= 0; i--)  
    { 
        output[count[arr[i] - min] - 1] = arr[i]; 
        count[arr[i] - min]--; 
    } 

    for (int i = 0; i < arr.length; i++) 
    { 
        arr[i] = output[i]; 
    }

This code is doing one extra work that it is also handling non-positive numbers.

#9

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