题解 | #最长回文子串#

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void (async function () {
    // Write your code here
    while ((line = await readline())) {
        let max = 0;
        let arr1 = line.split("");
        let arr2 = [];
        for (let i = 0; i < line.length - 1; i++) {
            let char = arr1.shift();
            //找回文数是奇数时，比如 ...cbabc... 这种情况
            max = Math.max(getCount(arr1, arr2) + 1, max);
            //找回文数为偶数时，比如 ...cbaabc... 这种情况
            arr2.unshift(char);
            max = Math.max(getCount(arr1, arr2), max);
        }
        console.log(max);
    }
})();

// 计算当前数组从左到右相同序列的项数和
var getCount = function (arr1 = [], arr2 = []) {
    let count = 0;
    let k = Math.min(arr1.length, arr2.length);
    for (let j = 0; j < k; j++) {
        if (arr2[j] != arr1[j]) {
            break;
        }
        count++;
    }
    return count * 2;
};