如何合并图形并共享同一个图例？

library(tidyverse)
library(ggplot2)
library(viridis)

plot1 <- ggplot(data = mpg, aes(x = displ, y = hwy, color = class)) +
  geom_point(size=1.7) + scale_color_viridis(discrete = T) + 
  theme_bw() + theme(panel.grid = element_blank())  
plot1

plot2 <- ggplot(data = mpg, aes(x = cty, y = hwy, color = class)) +
  geom_point(size=1.7) + scale_color_viridis(discrete = T) +
  theme_bw() + theme(panel.grid = element_blank())
plot2

library(patchwork)
plot1 + plot2

library(ggpubr)
ggarrange(plot1, plot2, common.legend = TRUE, legend="top")

library(cowplot)
combined_plot <- plot_grid(plot1 + theme(legend.position = 'none'), plot2 + theme(legend.position = 'none'), ncol = 2)
plot_grid(combined_plot, get_legend(plot1),rel_widths = c(4, 1))

library(patchwork)
plot1 + plot2 + plot_layout(guides = "collect") &
  theme(legend.position='bottom')