32. Longest Valid Parentheses

题意：求出最长的正确括号匹配长度

思路：定义一个match数组，遍历s,每出现一个’)‘若前面有’('匹配，则match[idx]=i 若无匹配，则match[i]=-1;

最后遍历一次s,每次match[i]==-1或者match[i]0&&s[i]’('时断开 if语句和最后的条件运算符返回最大长度

int longestValidParentheses(string s) {
		int match[100000];
		memset(match, 0, sizeof(match));
		int L_parentheses = 0;
		int R_parentheses = 0;
		for (int i = 0; i < s.length(); ++i) {
			if (s[i] == '(')++L_parentheses;
			else {
				if (!L_parentheses) {
					match[i] = -1;//means ) didnt match
					continue;
				}
				int idx = i - 1;
				while ((match[idx] !=0||s[idx]==')')&&idx>=0)--idx;
				if (idx >= 0) {//found
					match[idx] = i;//mark
				}
				--L_parentheses;
			}
		}
		int max_Length = 0;
		int temp_Length = 0;
		for (int i = 0; i < s.length(); ++i) {
			if (match[i] == -1 ||( match[i] == 0&&s[i]=='(')) {
				if(temp_Length>max_Length)max_Length = temp_Length;
				temp_Length = 0;
			}
			else ++temp_Length;
		}
		return max_Length>temp_Length?max_Length:temp_Length;
	}
	```