Algorithms – Rearrange the Array of Given Range N, such that A[i]=i.
Objective: Given a array of length N, in which elements are in the range of 1 to N. All elements may not present in the array. If element is not present , there will be -1 present in the array. Rearrange the array such that A[i]=i and if i is not present, display -1 at that place. See example
Approach: – Time Complexity -O(N), Space Complexity – O(1)
- Navigate the array.
- Check if element is -1, if yes then ignore it.
- If element is not -1, Check if its at it correct position (i=A[i]), If yes then ignore it.
- If element is not -1, and element is not at its correct position (i!=A[i]) then We need to place it to its correct position but there are two conditions
- Either A[i] is vacate, means A[i]=-1, then just put A[i]=i .
- OR A[i] is not vacate, means A[i]=x, then int y=x put A[i]=i. Now we need to place y to its correct place, so repeat from step 3. .
Fixed Indexed Array [-1, 1, 2, 3, 4, -1, 6, -1, -1, 9] Fixed Indexed Array [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]