To solve this problem, we can use a simple approach of using a hash map or dictionary data structure. Here are the steps:

1. Initialize a dictionary or hash map to store the frequency of each number in the array.

2. Iterate over the array. For each number, if it is already present in the dictionary, increment its frequency by 1. If it is not present, add it to the dictionary with frequency 1.

3. After iterating over the array, iterate over the dictionary. For each number, calculate the number of pairs that can be formed using its frequency. This can be done using the formula `n*(n-1)/2`, where `n` is the frequency of the number. This formula is derived from the combination formula which is used to calculate the number of ways to choose 2 items from `n` items.

4. Sum up the number of pairs for all numbers in the dictionary. This will be the total number of pairs of indices `(i, j)` such that `1≤i

Question

To solve this problem, we can use a simple approach of using a hash map or dictionary data structure. Here are the steps:

1. Initialize a dictionary or hash map to store the frequency of each number in the array.

2. Iterate over the array. For each number, if it is already present in the dictionary, increment its frequency by 1. If it is not present, add it to the dictionary with frequency 1.

3. After iterating over the array, iterate over the dictionary. For each number, calculate the number of pairs that can be formed using its frequency. This can be done using the formula `n*(n-1)/2`, where `n` is the frequency of the number. This formula is derived from the combination formula which is used to calculate the number of ways to choose 2 items from `n` items.

4. Sum up the number of pairs for all numbers in the dictionary. This will be the total number of pairs of indices `(i, j)` such that `1≤i<j≤n` and `ai xor aj=0`.

Here is a Python code snippet that implements the above steps:

```python
def count_pairs(arr):
    freq = {}
    for num in arr:
        if num in freq:
            freq[num] += 1
        else:
            freq[num] = 1

count = 0
    for num in freq:
        count += freq[num]*(freq[num]-1)//2

return count

n = int(input())
arr = list(map(int, input().split()))
print(count_pairs(arr))
```

In the above code, `count_pairs` function takes an array as input and returns the number of pairs of indices `(i, j)` such that `1≤i<j≤n` and `ai xor aj=0`. The input to the program is the number of elements in the array followed by the array elements. The output is the required number of pairs.

Knowee AI · Accepted Answer