R 如何自动统计列表中不同字符串的出现次数

我有一个约1000个条目的列表，其结构如下（小示例）：

示例
所有字符串
example <- list(
"1" =c("car","house"), 
"2" = c("family","work","car"), 
"3" = c("house","Work","car"),
"4" = "school", 
"5" = c("Car","school"))

all_strings <- tolower(unlist(example, use.names = FALSE))
#How many different string
length(unique(all_strings))
#[1] 5

#How often the different strings occur
all_string_listwise <- tolower(unlist(lapply(example, unique)))
table(all_string_listwise)

#all_string_listwise
#   car family  house school   work 
#     4      1      2      2      2