Previous Permutation With One Swap.py

# Runtime: 486 ms (Top 14.08%) | Memory: 15.3 MB (Top 47.61%)
class Solution:

    def find_max(self, i, a, n):
        maxs = i+1
        for j in range(n-1, i, -1):
            # if only j is greater than max and smaller than first descending element
            if(a[maxs] <= a[j] and a[j] < a[i]):
                maxs = j
        # Swap
        a[i], a[maxs] = a[maxs], a[i]
        return a

    def prevPermOpt1(self, arr):
        n = len(arr)
        for i in range(n-1, 0, -1):
            if(arr[i] < arr[i-1]):
                # sending the first descending element from right to max_function
                arr = self.find_max(i-1, arr, n)
                break
        return arr