【Leetcode】524. Longest Word in Dictionary through Deleting（最长子序列）

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.

题目大意：

找出d中满足于s的最长子序列，如果存在长度相同则返回字典序最小的字符串。

解题思路：

遍历d即可。

在判定是否为子序列时使用双指针。

bool isValid(string s, string target){
    int i=0, j=0;
    while(i<s.length() && j<target.length()){
        if(s[i] == target[j]){
            j++;
        }
        i++;
    }
    return j==target.length();
}

class Solution {
public:
    string findLongestWord(string s, vector<string>& d) {
        string logestWord = "";
        for(int i=0;i<d.size();i++){
            int l1 = logestWord.length(), l2 = d[i].length();
            if(l1 > l2 || (l1 == l2 && logestWord<d[i]) ){
                continue;
            }
            if(isValid(s, d[i])){
                logestWord = d[i];
            }
        }
        return logestWord;
    }
};