524. Longest Word in Dictionary through Deleting

Description

Given a string s and a string array dictionary, return the longest string in the dictionary that can be formed by deleting some of the given string characters. If there is more than one possible result, return the longest word with the smallest lexicographical order. If there is no possible result, return the empty string.

Example 1:

Input: s = "abpcplea", dictionary = ["ale","apple","monkey","plea"]
Output: "apple"

Example 2:

Input: s = "abpcplea", dictionary = ["a","b","c"]
Output: "a"

Constraints:

1 <= s.length <= 1000
1 <= dictionary.length <= 1000
1 <= dictionary[i].length <= 1000
s and dictionary[i] consist of lowercase English letters.

Solutions

Solution 1: Subsequence Judgment

We define a function $check(s, t)$ to determine whether string $s$ is a subsequence of string $t$. We can use a two-pointer approach, initializing two pointers $i$ and $j$ to point to the beginning of strings $s$ and $t$ respectively, then continuously move pointer $j$. If $s[i]$ equals $t[j]$, then move pointer $i$. Finally, check if $i$ equals the length of $s$. If $i$ equals the length of $s$, it means $s$ is a subsequence of $t$.

We initialize the answer string $ans$ as an empty string. Then, we iterate through each string $t$ in the array $dictionary$. If $t$ is a subsequence of $s$, and the length of $t$ is greater than the length of $ans$, or the length of $t$ is equal to the length of $ans$ but $t$ is lexicographically smaller than $ans$, then we update $ans$ to $t$.

The time complexity is $O(d \times (m + n))$, where $d$ is the length of the string list, and $m$ and $n$ are the lengths of string $s$ and the average length of strings in the list, respectively. The space complexity is $O(1)$.

Python3JavaC++GoTypeScriptRust

class Solution:
    def findLongestWord(self, s: str, dictionary: List[str]) -> str:
        def check(s: str, t: str) -> bool:
            m, n = len(s), len(t)
            i = j = 0
            while i < m and j < n:
                if s[i] == t[j]:
                    i += 1
                j += 1
            return i == m

        ans = ""
        for t in dictionary:
            if check(t, s) and (len(ans) < len(t) or (len(ans) == len(t) and ans > t)):
                ans = t
        return ans

class Solution {
    public String findLongestWord(String s, List<String> dictionary) {
        String ans = "";
        for (String t : dictionary) {
            int a = ans.length(), b = t.length();
            if (check(t, s) && (a < b || (a == b && t.compareTo(ans) < 0))) {
                ans = t;
            }
        }
        return ans;
    }

    private boolean check(String s, String t) {
        int m = s.length(), n = t.length();
        int i = 0;
        for (int j = 0; i < m && j < n; ++j) {
            if (s.charAt(i) == t.charAt(j)) {
                ++i;
            }
        }
        return i == m;
    }
}

class Solution {
public:
    string findLongestWord(string s, vector<string>& dictionary) {
        string ans = "";
        auto check = [&](const string& s, const string& t) {
            int m = s.size(), n = t.size();
            int i = 0;
            for (int j = 0; i < m && j < n; ++j) {
                if (s[i] == t[j]) {
                    ++i;
                }
            }
            return i == m;
        };
        for (auto& t : dictionary) {
            int a = ans.size(), b = t.size();
            if (check(t, s) && (a < b || (a == b && ans > t))) {
                ans = t;
            }
        }
        return ans;
    }
};

func findLongestWord(s string, dictionary []string) string {
    ans := ''
    check := func(s, t string) bool {
        m, n := len(s), len(t)
        i := 0
        for j := 0; i < m && j < n; j++ {
            if s[i] == t[j] {
                i++
            }
        }
        return i == m
    }
    for _, t := range dictionary {
        a, b := len(ans), len(t)
        if check(t, s) && (a < b || (a == b && ans > t)) {
            ans = t
        }
    }
    return ans
}

function findLongestWord(s: string, dictionary: string[]): string {
    const check = (s: string, t: string): boolean => {
        const [m, n] = [s.length, t.length];
        let i = 0;
        for (let j = 0; i < m && j < n; ++j) {
            if (s[i] === t[j]) {
                ++i;
            }
        }
        return i === m;
    };
    let ans: string = '';
    for (const t of dictionary) {
        const [a, b] = [ans.length, t.length];
        if (check(t, s) && (a < b || (a === b && ans > t))) {
            ans = t;
        }
    }
    return ans;
}

impl Solution {
    pub fn find_longest_word(s: String, dictionary: Vec<String>) -> String {
        let mut ans = String::new();
        for t in dictionary {
            let a = ans.len();
            let b = t.len();
            if Self::check(&t, &s) && (a < b || (a == b && t < ans)) {
                ans = t;
            }
        }
        ans
    }

    fn check(s: &str, t: &str) -> bool {
        let (m, n) = (s.len(), t.len());
        let mut i = 0;
        let mut j = 0;
        let s: Vec<char> = s.chars().collect();
        let t: Vec<char> = t.chars().collect();

        while i < m && j < n {
            if s[i] == t[j] {
                i += 1;
            }
            j += 1;
        }
        i == m
    }
}

524. Longest Word in Dictionary through Deleting

Description

Solutions

Solution 1: Subsequence Judgment

Comments