rt，C++打的过了，不知道为啥JS的T掉了。

"use strict";
const inpStr=new Int8Array(require('fs').readFileSync('/dev/stdin'));
const inpLen=inpStr.length;
let inpPtr=0;
function getNum(){
    let x=0,f=1;
    while(inpPtr<inpLen&&(inpStr[inpPtr]<48||inpStr[inpPtr]>57)){
        if(inpStr[inpPtr]==45)f=-1;
        inpPtr++;
    }
    if(inpPtr>=inpLen)return NaN;
    while(inpPtr<inpLen&&inpStr[inpPtr]>=48&&inpStr[inpPtr]<=57){
        x=x*10+inpStr[inpPtr]-48;
        inpPtr++;
    }
    return x*f;
}
const MAXM=1000000;
let n=0,m=0,vr=0,op=0,loc=0,vl=0;
const SIZ=(1<<21|9)+MAXM*21;
let lch=new Int32Array(SIZ+10);
let rch=new Int32Array(SIZ+10);
let num=new Int32Array(SIZ+10);
let totSeg=0;
function newSeg(idx){
    totSeg++;
    if(idx!==undefined){
        lch[totSeg]=lch[idx];
        rch[totSeg]=rch[idx];
        num[totSeg]=num[idx];
    }
    return totSeg;
}
let verRt=new Int32Array(MAXM+10);
let totVer=0;
function newVer(old,cop){
    totVer++;
    if(!cop)verRt[totVer]=verRt[old];
    else verRt[totVer]=newSeg(verRt[old]);
}
function _build_(rt,l,r){
    if(l==r){
        num[rt]=getNum();
        return;
    }
    let mid=(l+r)>>1;
    lch[rt]=newSeg();
    _build_(lch[rt],l,mid);
    rch[rt]=newSeg();
    _build_(rch[rt],mid+1,r);
}
function build(){
    verRt[0]=newSeg();
    _build_(verRt[0],1,n);
}
function _posChn_(rt,l,r,pos,val){
    if(l==r){
        num[rt]=val;
        return;
    }
    let mid=(l+r)>>1;
    if(pos<=mid){
        lch[rt]=newSeg(lch[rt]);
        _posChn_(lch[rt],l,mid,pos,val);
    }
    else{
        rch[rt]=newSeg(rch[rt]);
        _posChn_(rch[rt],mid+1,r,pos,val);
    }
}
function posChn(ver,pos,val){
    newVer(ver,true);
    _posChn_(verRt[totVer],1,n,pos,val);
}
function _posVal_(rt,l,r,pos){
    if(l==r)return num[rt];
    let mid=(l+r)>>1;
    if(pos<=mid)return _posVal_(lch[rt],l,mid,pos);
    else return _posVal_(rch[rt],mid+1,r,pos);
}
function posVal(ver,pos){
    newVer(ver,false);
    return _posVal_(verRt[totVer],1,n,pos);
}
function main(){
    n=getNum(),m=getNum();
    build();
    while(m--){
        vr=getNum(),op=getNum(),loc=getNum();
        if(op==1){
            vl=getNum();
            posChn(vr,loc,vl);
        }
        else console.log(posVal(vr,loc));
    }
}
main();