题解 | #密码截取#

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
    const line = await readline();
    if (line !== "") {
        let l = findMostLong(line);
        console.log(l);
    }
})();

function isValid(s) {
    if (s.length === 1) return true;
    let mid = s.length / 2;
    if (2 * mid === s.length) {
        for (let i = 0; i < mid; i++) {
            if (s.charAt(i) !== s.charAt(s.length - 1 - i)) {
                return false;
            }
        }
    } else {
        for (let i = 0; i < mid; i++) {
            if (s.charAt(i) !== s.charAt(s.length - 1 - i)) {
                return false;
            }
        }
    }
    return true;
}
//  f(0,n) = max( f(0,n-1) f(1,n) )
//  
function findMostLong(line) {
    let data = [];
    for (let i = 0; i < line.length; i++) {
        data[i] = [];
        for (let j = i; j > -1; j--) {
            if (isValid(line.substring(j, i + 1))) {
                data[i][j] = line.substring(j, i + 1).length;
            } else {
                data[i][j] = Math.max(data[i - 1][j], data[i][j + 1]);
            }
        }
    }
    return data[line.length - 1][0];
}