problem0032

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32. Longest Valid Parentheses

题目

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.

For "(()", the longest valid parentheses substring is "()", which has length = 2.

Another example is ")()())", where the longest valid parentheses substring is "()()", which has length = 4.

解题思路

1.记录每个符号的状态，(一律对应于0；)如果能够和前面的配上对，就记录为2，否则，记录为0

) ( ( ) ( ) ) ) ( ( ( ( ( ) ) ) ) (

形成记录

0 0 0 2 0 2 2 0 0 0 0 0 0 2 2 2 2 0

2.从左往右检查record，如果record[i]==2，record[j]==0，且record[j+1:i]中没有0，则record[i]=1,record[j]=1，那么，上面的record就变成了

0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 0

3.统计record中，最多的连续为1的次数，就是结果。

总结

根据记录统计，往往是最清晰的