LeetCode | Regular Expression Matching
2016-08-16 10:07
357 查看
Implement regular expression matching with support for ‘.’ and ‘*’.
‘.’ Matches any single character.
‘*’ Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).
The function prototype should be:
bool isMatch(const char *s, const char *p)
Some examples:
isMatch(“aa”,”a”) → false
isMatch(“aa”,”aa”) → true
isMatch(“aaa”,”aa”) → false
isMatch(“aa”, “a*”) → true
isMatch(“aa”, “.*”) → true
isMatch(“ab”, “.*”) → true
isMatch(“aab”, “c*a*b”) → true
这道题咋一看也是无从下手,难不成写个DFA?
便捷的方法是使用DP
自己跟着方法推一遍会发现同LCS(Longest Common Subsequence)简直如出一辙
只是二者在状态变化的时候,正则匹配会复杂一点
边界需要注意的是dp[0][0]=true,即两个串同时为空的时候判定可以成功匹配
例如 空串和a*
另外需要对整个dp数组第一行进行初始化,也就是应对多个a*之类的相连接的情况。
算法时间复杂度O(n^2) 空间复杂度O(n^2)
‘.’ Matches any single character.
‘*’ Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).
The function prototype should be:
bool isMatch(const char *s, const char *p)
Some examples:
isMatch(“aa”,”a”) → false
isMatch(“aa”,”aa”) → true
isMatch(“aaa”,”aa”) → false
isMatch(“aa”, “a*”) → true
isMatch(“aa”, “.*”) → true
isMatch(“ab”, “.*”) → true
isMatch(“aab”, “c*a*b”) → true
这道题咋一看也是无从下手,难不成写个DFA?
便捷的方法是使用DP
自己跟着方法推一遍会发现同LCS(Longest Common Subsequence)简直如出一辙
只是二者在状态变化的时候,正则匹配会复杂一点
边界需要注意的是dp[0][0]=true,即两个串同时为空的时候判定可以成功匹配
例如 空串和a*
另外需要对整个dp数组第一行进行初始化,也就是应对多个a*之类的相连接的情况。
算法时间复杂度O(n^2) 空间复杂度O(n^2)
class Solution { public: bool isMatch(string s, string p) { bool dp[s.size()+1][p.size()+1]; memset(dp,0,sizeof(dp)); dp[0][0]=true; //对第一行进行初始化 for(int i=1;i<=p.size();i++){ if(p[i-1]=='*'){ dp[0][i]=dp[0][i-2]; } } for(int i=1;i<=s.size();i++){ for(int j=1;j<=p.size();j++){ if(p[j-1]=='.' || p[j-1]==s[i-1]){ dp[i][j]=dp[i-1][j-1]; } else if(p[j-1]=='*'){ dp[i][j]=dp[i][j-2]; if(p[j-2]=='.' || s[i-1]==p[j-2]) dp[i][j]|=dp[i-1][j]; } else{ dp[i][j]=false; } } } return dp[s.size()][p.size()]; // return isMatch(s.c_str(),p.c_str()); } } }
相关文章推荐
- [LeetCode] Regular Expression Matching [6]
- 刷LeetCode(10)——Regular Expression Matching
- [LeetCode] Regular Expression Matching
- [LeetCode] Regular Expression Matching [6]
- LeetCode : Regular Expression Matching
- [Leetcode] Regular expression matching 正则表达式匹配
- leetcode Regular Expression Matching
- Leetcode 10: Regular Expression Matching
- Leetcode | Regular Expression Matching
- Leetcode——44Wildcard Matching && 10 Regular Expression Matchi
- [leetcode] 10 Regular Expression Matching
- Regular Expression Matching LeetCode
- [Leetcode]_10 Regular Expression Matching
- LeetCode 10 - Regular Expression Matching
- leetcode--010 Regular Expression Matching
- 【leetcode刷题笔记】Regular Expression Matching
- 【LeetCode】10. Regular Expression Matching
- leetcode----Regular Expression Matching
- [LeetCode] Regular Expression Matching
- Leetcode 10 - Regular Expression Matching