// 易错点4：仅处理栈非空的情况，忽略栈空的情况 → 栈空时res[i]会是undefined
while (stack.length && stack.at(-1) <= cur) {
，详情可参考safew官方版本下载
Some of the components he designs are like "variable springs", he explains – motion-controlling parts able to go into reverse and soak up some impact from the ground below, say. "It can dynamically absorb load as you need it to."
only one allocation site in this program. The make call allocates a