524. Longest Word in Dictionary through Deleting

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

Example 1:

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

Output: 
"apple"

Example 2:

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

Output: 
"a"

Note:

1. All the strings in the input will only contain lower-case letters.
2. The size of the dictionary won't exceed 1,000.
3. The length of all the strings in the input won't exceed 1,000.

 AC code:

class Solution {
public:
    string findLongestWord(string s, vector<string>& d) {
        string ans = "";
        string temp;
        sort(d.begin(), d.end());
        for (int i = 0; i < d.size(); ++i) {
            temp = helper(s, d[i]);
            ans = temp.length() > ans.length() ? temp : ans;
        }
        return ans;
    }
    
private:
    string helper(string s, string d) {
        int len = s.length();
        int i, j;
        for (i = 0, j = 0; i < len && j < s.length();) {
            if (s[i] == d[j]) i++, j++;
            else i++;
        }
        if (j == d.length()) return d;
        else return "";
    }
};

Runtime: 76 ms, faster than 58.66% of C++ online submissions for Longest Word in Dictionary through Deleting.

Approach #2：Using Java without sort

public class Solution {
    public boolean isSubsequence(String x, String y) {
        int j = 0;
        for (int i = 0; i < y.length() && j < x.length(); i++)
            if (x.charAt(j) == y.charAt(i))
                j++;
        return j == x.length();
    }
    public String findLongestWord(String s, List < String > d) {
        String max_str = "";
        for (String str: d) {
            if (isSubsequence(str, s)) {
                if (str.length() > max_str.length() || (str.length() == max_str.length() && str.compareTo(max_str) < 0))
                    max_str = str;
            }
        }
        return max_str;
    }
}

Runtime: 18 ms, faster than 90.03% of Java online submissions for Longest Word in Dictionary through Deleting.