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.
使用动态规划的思想，从后往前求解，遇到“（”,则进行条件判断。public int longestValidParentheses(String s) { if (s == null || s.length() == 0 || s.length() == 1) { return 0; } int len = s.length(); int[] num = new int[len]; num[len - 1] = 0; for (int i = len - 2; i >= 0; i--) { if (s.charAt(i) == '(') { int j = i + 1 + num[i + 1]; if (j < len && s.charAt(j) == ')') { num[i] = num[i + 1] + 2; if (j + 1 < len) { num[i] += num[j + 1]; } } } } int max = 0; for (int i = 0; i < len; i++) { if (max < num[i]) { max = num[i]; } } return max; }
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原文：http://blog.csdn.net/u010378705/article/details/31345739