Plot ASCII chart for time-price pairs

Given an unsorted array of (timestamp, price) integer pairs, write a function to render an ASCII chart of the time series. The x-axis must include every integer timestamp from the minimum to the maximum in ascending order; the y-axis must include every integer price from the maximum down to the minimum. Represent each observed (timestamp, price) point with a '' in its cell. Draw a rectangular frame with '+' at borders; the top and bottom borders consist of repeated "+-----" segments separated by '+', one segment per timestamp column. Each interior row begins and ends with '+', with spaces in between except where a '' appears. If multiple points fall in the same cell, show one '*'. If a timestamp or price level has no point, leave its cell blank. Return the chart as a list of strings. For example, input [(1, 2), (6, 3), (4, 5), (2, 2)] should produce a chart whose columns map to timestamps 1..6 and rows to prices 5..2. Explain your approach and analyze time and space complexity.