SOURCE

function firstLargeNum(num) {
    let i = 0;
    let ans = [], stack = [];
    for (i = num.length - 1; i >= 0; i--) {
        while (stack.length > 0) {
            let top = stack[stack.length - 1];
            if (top > num[i]) {
                ans.unshift(top);
                break;
            } else {
                stack.pop();
            }
        }
        if (stack.length === 0) {
            ans.unshift(-1);
        }
        stack.push(num[i]);
    }
    return ans;
}
console.log(firstLargeNum([3, 2, 1, 2, 6, 2, 3]));