[LeetCode][JavaScript]Regular Expression Matching
Regular Expression Matching
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
https://leetcode.com/problems/regular-expression-matching/
第一轮遍历,把p整理成容易处理的格式,这一步不做直接处理也行。
如输入c*a*b, regMap -> ["c*", "a*", b]
然后就是花式递归,分成以下几种情况:
1. 正则数组中为单个字符,字符串的第一个必须与之匹配
2. 正则数组中包含*,枚举递归。
比如isMatch("aab", ".*b"),
当"aab"碰到".*"的时候,枚举三种情况:("aab", "b"), ("ab", ".*b"), ("b", ".*b"), ("", ".*b")
3. 当找完最后一个正则的时候,如果字符串正好用完,此时就是正确的结果,返回true。
1 /** 2 * @param {string} s 3 * @param {string} p 4 * @return {boolean} 5 */ 6 var isMatch = function(s, p) { 7 var regMap = []; 8 buildMap(regMap, p); 9 return matchReg(s, 0); 10 11 function buildMap(map, reg){ 12 for(var i = 0; i < reg.length; i++){ 13 if(reg[i] === '*'){ 14 if(map.length >= 1){ 15 map[map.length - 1] = map[map.length - 1] + "*"; 16 } 17 }else{ 18 map.push(reg[i]); 19 } 20 } 21 } 22 function matchReg(str, index){ 23 if(index === regMap.length){ 24 return str === "" ? true : false; 25 } 26 27 //single char 28 if(regMap[index].indexOf('*') === -1){ 29 if(str[0] === regMap[index] || (regMap[index] === "." && str != "")){ 30 return matchReg(str.substring(1, str.length), index + 1); 31 }else{ 32 return false; 33 } 34 } 35 36 //.* a* 37 while(str !== "" && (str[0] === regMap[index][0] || regMap[index][0] === ".")){ 38 if(matchReg(str, index + 1)){ 39 return true; 40 } 41 str = str.substring(1, str.length); 42 } 43 44 return matchReg(str, index + 1); 45 } 46 };
一组Test Cases
1 function test(){ 2 console.log(isMatch("a", "ab*")); //true 3 console.log(isMatch("aa", "aa")); //true 4 console.log(isMatch("aa", "a*")); //true 5 console.log(isMatch("aa", ".*")); //true 6 console.log(isMatch("ab", ".*")); //true 7 console.log(isMatch("aab", "c*a*b")); //true 8 9 console.log(isMatch("aa", "a")); //false 10 console.log(isMatch("aaa", "aa")); //false 11 console.log(isMatch("ab", ".*c")); //false 12 console.log(isMatch("a", ".*..a*")); //false 13 }