文章目录
- 5. 最长回文子串
- 516. 最长回文子序列
5. 最长回文子串
- dp[i][j]:s[i-j]是否是回文串
string longestPalindrome(string s) {
int n = s.size();
vector<vector<bool>> dp(n, vector<bool>(n ,false));
for(int i = 0; i < n; i++) dp[i][i] = true;
int startIdx = 0;
int maxLen = 1;
for(int len = 2; len <= n; len++){
for(int i = 0; i <= n - len; i++){
int j = i + len - 1;
if(s[i] == s[j]){
if(len < 4 || dp[i + 1][j - 1]){
dp[i][j] = true;
}
if(dp[i][j] && maxLen < len){
maxLen = len;
startIdx = i;
}
}
}
}
return s.substr(startIdx, maxLen);
}
516. 最长回文子序列
- dp[i][j]:s[i-j]区间内回文子序列的长度
int longestPalindromeSubseq(string s) {
int n = s.size();
vector<vector<int>> dp(n, vector<int>(n, 0));
for(int i = 0; i < n; i++) dp[i][i] = 1;
for(int len = 2; len <= n; len++){
for(int i = 0; i <= n - len; i++){
int j = i + len - 1;
if(s[i] == s[j]) dp[i][j] = dp[i + 1][j - 1] + 2;
else dp[i][j] = max(dp[i + 1][j], dp[i][j - 1]);
}
}
return dp[0][n - 1];
}