message: Update previous-permutation-with-one-swap.cpp
diff: class Solution {
  public:
  vector<int> prevPermOpt1(vector<int>& A) {
  - int left = A.size() - 2, right = A.size() - 1;
  + int left = A.size() - 2;
  for (; left >= 0 && A[left] <= A[left + 1]; --left);
  if (left < 0) {
  return A;
  }
  + int right = A.size() - 1;
  for (; A[left] <= A[right]; --right);
  for (; A[right - 1] == A[right]; --right);
  swap(A[left], A[right]);
  