leetcode-32-最長有效括號

解1：動態規劃

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// @lc code=start
/**
 * @param {string} s
 * @return {number}
 */
var longestValidParentheses = function(s) {
    const sLen = s.length;
    if (!sLen) return 0;
    let dp = new Array(sLen).fill(0);
    dp[-1] = 0;
    s.split('').forEach((val, i) => {
        let j = i - dp[i - 1] - 1;
        if (val == ')' && j >= 0 && s[j] == '(') {
            dp[i] = dp[i - 1] + dp[j - 1] + 2;
        }
    });

    return Math.max(...dp);
};

console.log(longestValidParentheses("()(())"));    // 6
// @lc code=end

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解2：棧

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var longestValidParentheses = function(s) {
    let stack = [-1];
    let len = 0;
    let maxLen = 0;
    s.split('').forEach((val, i) => {
        if (val == '(') {
            stack.push(i);
        } else {
            stack.pop();
            if (stack.length == 0) {
                stack.push(i);
            } else {
                len = i - stack[stack.length - 1];
                maxLen = Math.max(len, maxLen);
            }
        }
    });
    return maxLen;
};

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