Rust Gym Leetcode 1754 Largest Merge Of Two Strings Rust Solution

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);
}