题解 | 元素方碑

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 i = 0;
    while ((line = await readline())) {
        if (i > 1 && i % 2 === 0) {
            const arr = line.split(" ");
            const sum = arr.reduce((a, b) => +a + +b, 0);
            if (arr.length === 1) {
                console.log("YES");
            }else if(arr.length === 2){
                if(+arr[0] === +arr[2]){
                    console.log("YES")
                }else{
                    console.log("NO")
                }
            } else if (sum % arr.length === 0) {
                const f = sum / arr.length;
                const oddArr = [],
                    evenArr = [];
                for (let i = 0; i < arr.length; i++) {
                    if ((i + 1) % 2 === 0) {
                        oddArr.push(arr[i]);
                    } else {
                        evenArr.push(arr[i]);
                    }
                }
                if (
                    oddArr.reduce((a, b) => +a + +b, 0) / oddArr.length === f &&
                    evenArr.reduce((a, b) => +a + +b, 0) / evenArr.length === f
                ) {
                    console.log("YES");
                } else {
                    console.log("NO");
                }
            } else {
                console.log("NO");
            }
        }
        i++;
    }
})();