题解 | 小红的双生串

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
    let line = await readline();
    console.log(getDouble(line));
})();

function getDouble(str) {
    const frontMap = {};
    const endMap = {};

    for (let i = 0; i < str.length / 2; i++) {
        frontMap[str[i]] = frontMap[str[i]] ? frontMap[str[i]] + 1 : 1;
    }
    for (let i = str.length / 2; i < str.length; i++) {
        endMap[str[i]] = endMap[str[i]] ? endMap[str[i]] + 1 : 1;
    }

    const frontKeys = Object.keys(frontMap)
    const endKeys = Object.keys(endMap)
    if (frontKeys.length === 1 && endKeys.length === 1) return 0
    
    let max = 0
    let result = 0
    for (const key of frontKeys) {
        max = frontMap[key] > max ? frontMap[key] : max
    }
    result += str.length / 2 - max
    max = 0
    for (const key of endKeys) {
        max = endMap[key] > max ? endMap[key] : max
    }
    result += str.length / 2 - max
    return result
}