description:
Given an input string (s) and a pattern (p), 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).
Note:
s could be empty and contains only lowercase letters a-z.
p could be empty and contains only lowercase letters a-z, and characters like . or *.
Example 1:
Input:
s = "aa"
p = "a"
Output: false
Explanation: "a" does not match the entire string "aa".
Example 2:
Input:
s = "aa"
p = "a*"
Output: true
Explanation: '*' means zero or more of the precedeng element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".
Example 3:
Input:
s = "ab"
p = ".*"
Output: true
Explanation: ".*" means "zero or more (*) of any character (.)".
Example 4:
Input:
s = "aab"
p = "c*a*b"
Output: true
Explanation: c can be repeated 0 times, a can be repeated 1 time. Therefore it matches "aab".
Example 5:
Input:
s = "mississippi"
p = "mis*is*p*."
Output: false
my answer:
可以看出代码逻辑就是讨论pattern从0->2,
等于2时又分为第二个是不是无限匹配
最后还要处理一个‘’和p匹配的问题
大佬的answer:
class Solution {
public:
bool isMatch(string s, string p) {
if (p.empty()) return s.empty();
if (p.size() == 1) {
return (s.size() == 1 && (s[0] == p[0] || p[0] == '.'));
}
if (p[1] != '*') {
if (s.empty()) return false;
return (s[0] == p[0] || p[0] == '.') && isMatch(s.substr(1), p.substr(1));
//这句话在写(抄)代码的时候报错了,根据控制变量法,最后判定错误出在&&,
//因为我在模仿大佬的codestyle的时候&&右边打了两个空格(也可能是当时按错了输入法变
//成了全角emmmmm)
}
while (!s.empty() && (s[0] == p[0] || p[0] == '.')) {
if (isMatch(s, p.substr(2))) return true;
s = s.substr(1);
}
return isMatch(s, p.substr(2));
}
};
relative point get√:
hint :
关键在于数清可能遇到的可能情况,就感觉easy考的都是基础的数据结构,越难就越考逻辑清晰,缜密,咋才能考虑到所有情况?--> 靠bug >o<!!!