因为没有马蹄钉,一个王国就消失了,或者俗话说.

给出一个输入列表,生成相关的谚语.例如,

• 给定列表["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]
• 你将输出这个谚语的全文:

For want of a nail the shoe was lost.
For want of a shoe the horse was lost.
For want of a horse the rider was lost.
For want of a rider the message was lost.
For want of a message the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a nail.

请注意,输入列表可能会有所不同; 您的解决方案应该能够处理任意长度和内容的列表。输出文本的行不应该是静态的、不变的字符串; 所有的都应该根据给定的输入而变化.

Wikipedia http://en.wikipedia.org/wiki/For_Want_of_a_Nail

pub fn build_proverb(list: Vec<&str>) -> String {
   unimplemented!("build a proverb from this list of items: {:?}", list)
}

# #![allow(unused_variables)]
#fn main() {
#[test]
fn test_two_pieces() {
   let input = vec!["nail", "shoe"];
   let expected = vec![
       "For want of a nail the shoe was lost.",
       "And all for the want of a nail.",
   ]
   .join("\n");
   assert_eq!(build_proverb(input), expected);
}

// Notice the change in the last line at three pieces.
#[test]
//#[ignore]
fn test_three_pieces() {
   let input = vec!["nail", "shoe", "horse"];
   let expected = vec![
       "For want of a nail the shoe was lost.",
       "For want of a shoe the horse was lost.",
       "And all for the want of a nail.",
   ]
   .join("\n");
   assert_eq!(build_proverb(input), expected);
}

#[test]
//#[ignore]
fn test_one_piece() {
   let input = vec!["nail"];
   let expected = String::from("And all for the want of a nail.");
   assert_eq!(build_proverb(input), expected);
}

#[test]
//#[ignore]
fn test_zero_pieces() {
   let input: Vec<&str> = vec![];
   let expected = String::new();
   assert_eq!(build_proverb(input), expected);
}

#[test]
//#[ignore]
fn test_full() {
   let input = vec![
       "nail", "shoe", "horse", "rider", "message", "battle", "kingdom",
   ];
   let expected = vec![
       "For want of a nail the shoe was lost.",
       "For want of a shoe the horse was lost.",
       "For want of a horse the rider was lost.",
       "For want of a rider the message was lost.",
       "For want of a message the battle was lost.",
       "For want of a battle the kingdom was lost.",
       "And all for the want of a nail.",
   ]
   .join("\n");
   assert_eq!(build_proverb(input), expected);
}

#[test]
//#[ignore]
fn test_three_pieces_modernized() {
   let input = vec!["pin", "gun", "soldier", "battle"];
   let expected = vec![
       "For want of a pin the gun was lost.",
       "For want of a gun the soldier was lost.",
       "For want of a soldier the battle was lost.",
       "And all for the want of a pin.",
   ]
   .join("\n");
   assert_eq!(build_proverb(input), expected);
}

#}

# #![allow(unused_variables)]
#fn main() {
pub fn build_proverb(items: Vec<&str>) -> String {
   let mut stanzas = Vec::with_capacity(items.len());
   for index in 0..items.len() {
       if index == items.len() - 1 {
           stanzas.push(format!("And all for the want of a {}.", items[0]));
       } else {
           stanzas.push(format!(
               "For want of a {} the {} was lost.",
               items[index],
               items[index + 1]
           ));
       }
   }
   stanzas.join("\n")
}

#}