cassidoo_dec_22_2025_2.js

/* solution */

const validate = ([y, z, ...rest]) =>
    rest.length
        ? (rest.shift() === y && validate([z, y, ...rest]))
        : true;



/* testing */

function assert(input, expected) {

    const actual = validate(input);
    if (actual !== expected) {
        console.error("FAIL", input, "(expected", expected, ")");
    } else {
        console.log("PASS", input);
    }
}

assert([], true);
assert([1], true);
assert([1,1], true);
assert([1,2,1], true);
assert([10,5,10,5,10], true);
assert([2,2,3,3], false);
assert([5,4,3,5,4,3], false);