在向量中交换两个值

I'm trying to find the most left point on a graph of a random set of points. For Example, out of the points (3, 5) (5, 2) (8, 7) (1, 3), the most left point would be (1, 3). Once I do this, I have to put the most left point in spot 0 of a vector. I am having trouble switching two variables since I don't know which spot mostLeft is originally from. mostLeft is a node containing two ints. I'm trying to find the most left point on a gra