1754. Largest Merge Of Two Strings

You are given two strings `word1` and `word2`. You want to construct a string `merge` in the following way: while either `word1` or `word2` are non-empty, choose one of the following options:

• If `word1` is non-empty, append the first character in `word1` to `merge` and delete it from `word1`.
• For example, if `word1 = "abc" `and `merge = "dv"`, then after choosing this operation, `word1 = "bc"` and `merge = "dva"`.
• If `word2` is non-empty, append the first character in `word2` to `merge` and delete it from `word2`.
• For example, if `word2 = "abc" `and `merge = ""`, then after choosing this operation, `word2 = "bc"` and `merge = "a"`.

Return the lexicographically largest `merge` you can construct.

A string `a` is lexicographically larger than a string `b` (of the same length) if in the first position where `a` and `b` differ, `a` has a character strictly larger than the corresponding character in `b`. For example, `"abcd"` is lexicographically larger than `"abcc"` because the first position they differ is at the fourth character, and `d` is greater than `c`.

Example 1:

```Input: word1 = "cabaa", word2 = "bcaaa"
Output: "cbcabaaaaa"
Explanation: One way to get the lexicographically largest merge is:
- Take from word1: merge = "c", word1 = "abaa", word2 = "bcaaa"
- Take from word2: merge = "cb", word1 = "abaa", word2 = "caaa"
- Take from word2: merge = "cbc", word1 = "abaa", word2 = "aaa"
- Take from word1: merge = "cbca", word1 = "baa", word2 = "aaa"
- Take from word1: merge = "cbcab", word1 = "aa", word2 = "aaa"
- Append the remaining 5 a's from word1 and word2 at the end of merge.
```

Example 2:

```Input: word1 = "abcabc", word2 = "abdcaba"
Output: "abdcabcabcaba"
```

Constraints:

• `1 <= word1.length, word2.length <= 3000`
• `word1` and `word2` consist only of lowercase English letters.

1754. Largest Merge Of Two Strings
``````struct Solution;

impl Solution {
fn largest_merge(word1: String, word2: String) -> String {
Solution::merge(&word1, &word2)
}

fn merge(w1: &str, w2: &str) -> String {
if w1.is_empty() || w2.is_empty() {
format!("{}{}", w1, w2)
} else {
if w1 > w2 {
format!("{}{}", &w1[0..1], Solution::merge(&w1[1..], w2))
} else {
format!("{}{}", &w2[0..1], Solution::merge(w1, &w2[1..]))
}
}
}
}

#[test]
fn test() {
let word1 = "cabaa".to_string();
let word2 = "bcaaa".to_string();
let res = "cbcabaaaaa".to_string();
assert_eq!(Solution::largest_merge(word1, word2), res);
let word1 = "abcabc".to_string();
let word2 = "abdcaba".to_string();
let res = "abdcabcabcaba".to_string();
assert_eq!(Solution::largest_merge(word1, word2), res);
}
``````