Associate Professional

We're asked to traverse the array only once. We need to use two pointers/ variables to traverse the array. We have two options here:

Using two variables pointing from the beginning of the array
Using one variable pointing from the beginning and the other from the end.
Variables from both ends of the array:

Way to think:

We use two variables l and h storing the indexes of the array's first and last elements, respectively. We want to set 0's followed by 1's in the array. The elements traversed by l from the beginning should be 0's, and the elements from the end visited by h should be 1s. We need to swap the elements if l finds a 1 or h finds a 0.
int* segregation(int arr[], int n) 
{ 
int temp, l = 0; 
int h = n - 1; 
while(l < h) 
{ 
if(arr[l] == 0) 
{ 
l++; 
} 
else if(arr[h] == 1) 
{ 
h--; 
} 
else 
{ 
temp = arr[l]; 
arr[l] = arr[h]; 
arr[h] = temp; 
} 
} 
return arr; 
}
Both variables from the beginning of the array:

Way to think:

We want to arrange 0's followed by 1's in the array. We'll use two variables, both traversing from the beginning of the array. One variable is used to visit the elements and check the values, and the other is dedicated to staying at an index. The logic here is that whenever the visiting variable finds a 0, we should swap the elements at two variables.
nt* segregation(int arr[], int n) 
{ 
int i, j, temp; 
j = 0; 
for(i = 0; i < n; i++) 
{ 
if(arr[i] == 0) 
{ 
if(i != j) 
{ 
temp = arr[i]; 
arr[i] = arr[j]; 
arr[j] = temp; 
j++; 
} 
} 
} 
return arr;