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;

// 其实就是左右两边，分别找最大重复的字母的数量，然后用【总数 - 这个最大值】即可，接着两边相加就是答案
void async function () {
    const str = await readline()

    const frontMap = new Map()
    const backMap = new Map()

    for (let i = 0; i < str.length; i++) {
        if (i >= str.length / 2) {
            backMap.set(str[i], (backMap.get(str[i]) || 0) + 1)
        } else {
            frontMap.set(str[i], (frontMap.get(str[i]) || 0) + 1)
        }
    }

    const frontMax = str.length / 2 - Math.max(...Array.from(frontMap).map(item => item[1]))
    const backMax = str.length / 2 - Math.max(...Array.from(backMap).map(item => item[1]))

    console.log(frontMax + backMax)
}()