leetcode update

content/posts/leetcode.md

@@ -6757,3 +6757,53 @@ func reverseString(s []byte)  {
     }
 }
 ```
+
+## day98 2024-06-03
+### 2486. Append Characters to String to Make subsequence 
+You are given two strings s and t consisting of only lowercase English letters.
+
+Return the minimum number of characters that need to be appended to the end of s so that t becomes a subsequence of s.
+
+A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.
+
+Example 1:
+
+Input: s = "coaching", t = "coding"
+Output: 4
+Explanation: Append the characters "ding" to the end of s so that s = "coachingding".
+Now, t is a subsequence of s ("coachingding").
+It can be shown that appending any 3 characters to the end of s will never make t a subsequence.
+
+Example 2:
+
+Input: s = "abcde", t = "a"
+Output: 0
+Explanation: t is already a subsequence of s ("abcde").
+
+Example 3:
+
+Input: s = "z", t = "abcde"
+Output: 5
+Explanation: Append the characters "abcde" to the end of s so that s = "zabcde".
+Now, t is a subsequence of s ("zabcde").
+It can be shown that appending any 4 characters to the end of s will never make t a subsequence. 
+
+### 题解
+
+本题从字符串s中删除任意位置的字符后再在末尾添加任意字符得到t, 这里从s中删除字符的位置是任意的，也就意味着只要在s中从头遍历并找到t的一个最长可行前缀即可。再用t的长度减去s中已经存在的前缀的长度级可得到需要补充的后缀长度。
+
+### 代码
+
+```go 
+func appendCharacters(s string, t string) int {
+    prefix := 0
+    tlen := len(t)
+    t = t + "'"
+    for i,_ := range s{
+        if s[i] == t[prefix]{
+            prefix++
+        }
+    }
+    return tlen-prefix
+}
+```