Bucket sort ( doubt in code)

#1

From the above code
int m = s[i].marks;
v[m].push_back( s[i] );

How are we able to pushback so many marks at a single index of vector.

Please explain how is this happening ?

#2

Hello @ujj1804_1156aee80205d0bf,

vector<student>v[101];

This is an array of vectors, its structure looks like this:

index  -> vector<Student>
0      -> vector<Student>
1      -> vector<Student>
2      -> vector<Student>
3      -> vector<Student>
4      -> vector<Student>
.
.
.
100    -> vector<Student>

We are able to push back so many marks at a single index of the array because at each index there is a vector.

#3

So at each index of the vector , there is a vector (inner vector), if we want to access the content directly from the inner vector ,how can we do that without using for loop , i mean if we want to print content of a specific index of inner vector ?

#4

@ujj1804_1156aee80205d0bf,

So at each index of the vector
It’s at each index of the array.

basically, it’s like if you want to create a normal array of size 10 of type int then you use,

int arr[10]

Now, if you want to create an array of size 10 of type vector then you use,

vector<int> arr[10]

To access inner elements, just use arr[i][j];
i is array’s index and j is vector’s index.

#5

Sir in the above code the array is of type vector , but instead of 9 values (3 values at each index of array ) , its taking 3 values as input. Please tell why this is not taking 9 values as input as its the same syntax as written in the code i shared earlier ?

Suppose for input 1 2 3
i am getting output
1 0 0
2 0 0
3 0 0
which means that v[0][0],v[1][0], v[2][0] are getting initialized with the input and rest of the values automatically become zero.

#6

@ujj1804_1156aee80205d0bf,
Your code is wrong,

for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++){
cin>>n;
v[i].push_back(n);
}
}

Now try input,
1 2 3
4 5 6
7 8 9

#7

Thanks sir , but in the bucket sort code which i shared earlier why we were able to pushback the elements using only one for loop . As here we require 2 for loops for entering values.

#8

@ujj1804_1156aee80205d0bf,

Actually, in that code, we are just iterating over the student array and pushing the respective student name with index = student mark.

#9

Sir i have understood, i am very thankful to you for helping me and clearing the doubts.

1 Like
#10

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