Suppose we have a list of distinct numbers; we have to find the minimum number of swaps required to sort the list in increasing order.
So, if the input is like nums = [3, 1, 7, 5], then the output will be 2, as we can swap 3 and 1, then 5 and 7.
To solve this, we will follow these steps:
- sort_seq := sort the list nums
- table := a new map
- for each index i and value n in nums, do
- table[n] := i
- swaps := 0
- for i in range 0 to size of nums, do
- n := nums[i]
- s_n := sort_seq[i]
- s_i := table[s_n]
- if s_n is not same as n, then
- swaps := swaps + 1
- nums[s_i] := n
- nums[i] := s_n
- table[n] := s_i
- table[s_n] := i
- return swaps
Let us see the following implementation to get better understanding:
Example Code
class Solution: def solve(self, nums): sort_seq = sorted(nums) table = {} for i, n in enumerate(nums): table[n] = i swaps = 0 for i in range(len(nums)): n = nums[i] s_n = sort_seq[i] s_i = table[s_n] if s_n != n: swaps += 1 nums[s_i] = n nums[i] = s_n table[n] = s_i table[s_n] = i return swaps ob = Solution() nums = [3, 1, 7, 5] print(ob.solve(nums))
Input
[3, 1, 7, 5]
Output
2