数据突然duliu了

请问下面这两种有啥区别 为什么放前面就TLE？

ll dfs(int x,int in)
{
    if(x==t) return in;
    ll out=0;
    for(int &i=cur[x];i;i=edge[i].nxt)
    {
        int y=edge[i].to;
        if(dep[y]!=dep[x]+1||edge[i].val==0) continue;
        //if(!in) return out;放这就T
        int res=dfs(y,min(in,edge[i].val));
        edge[i].val-=res;
        edge[i^1].val+=res;
        in-=res;
        out+=res;
        if(!in) return out;//放这就过？？
    }
    if(out==0) dep[x]=0;
    return out;
}