随笔
随笔，聊天
博文
(2025-03-22 07:23:19)
ZT匈牙利数学家波利亚(GeorgePólya)曾经讲过一个跟黎曼猜想有关的小故事，故事的主角是英国数学家哈代与丹麦数学家玻尔。这两位在黎曼猜想研究中作出过成果的数学家当然都对黎曼猜想怀有浓厚兴趣。有一段时间，哈代常常利用假期访问玻尔，一起讨论黎曼猜想，直到假期将尽才匆匆赶回英国。结果有一次，当哈代又必须匆匆赶回英国时，很不幸地发现码头上只剩下一[阅读全文]
(2025-03-14 05:07:56)
(2024-01-25 03:23:31)
1.publicstaticStringremoveBlankAndDot(Stringtarget){if(target!=null){intlen=target.length();//movethisoutofloop,moreefficientStringBufferbuf=newStringBuffer(len);//usingknownsizetocreateStringBuffer,moreefficient,defaultsizeis16char.//Ifthelen>16,incorrectdesignwillforceStringBuffertoresize.//Usingpre-sizeCollectionsismoreefficient,forexample://faster,assumingexpecting1000-2000elements://Mapm=n...[阅读全文]
(2024-01-25 03:11:53)
1.publicstaticStringremoveBlankAndDot(Stringtarget){if(target!=null){StringBufferbuf=newStringBuffer();for(intii=0;ii<target.length();ii++){charc=target.charAt(ii);if(c!=''&&c!='.')buf.append(c);}returnbuf.toString();}returnnull;}2.publicclassDataLogger{privatestaticPrintStreamerr=System.err;privatestaticStringfilePath="log";privatestaticStringfileName="my...[阅读全文]
(2024-01-25 03:05:44)
1..class{
padding-left:3px;
margin-right:6px;
padding-top:10px;
padding-right:9px;
margin-left:6px;
background-image:url('images/happy.jpg');
background-position:bottom;
background-repeat:repeat-x;
background-color:#E2CCCC;
}
-------------------------------
CSSShorthandisusedtoturnmanyCSSpropertiesintoonetomakethefilesizesmaller
andaclean...[阅读全文]
padding-left:3px;
margin-right:6px;
padding-top:10px;
padding-right:9px;
margin-left:6px;
background-image:url('images/happy.jpg');
background-position:bottom;
background-repeat:repeat-x;
background-color:#E2CCCC;
}
-------------------------------
CSSShorthandisusedtoturnmanyCSSpropertiesintoonetomakethefilesizesmaller
andaclean...[阅读全文]
(2024-01-18 05:59:56)
1.
varPerson={
"firstname":"Mike",
"middlename":"D.",
...,
}
for(variteminPerson){
document.writeln(Person[item]);
}
------------------------------------
for-inloopisusedtoiterateovernonarrayobject.
Itmakesnoguaranteeabouttheorderofenumerateditem.
Forsequentialintegers,weshoulduseanarray;otherwise,useanobject.<...[阅读全文]
varPerson={
"firstname":"Mike",
"middlename":"D.",
...,
}
for(variteminPerson){
document.writeln(Person[item]);
}
------------------------------------
for-inloopisusedtoiterateovernonarrayobject.
Itmakesnoguaranteeabouttheorderofenumerateditem.
Forsequentialintegers,weshoulduseanarray;otherwise,useanobject.<...[阅读全文]
(2024-01-18 05:49:02)
CANDC++TESTING(INTERMEDIATE)1.Explainthefollowing:(1)structstr*(*block())[8];(2)double(*(*func)())[2][6];2.What'sobjectID?What'spersistentobject?Howtocreatepersistentobject?3.What’sthetype(span)ofapointer?Inthefollowingcode:classA:publicB{…};Aa;B*pb=&a;A*pa=&a;What’sdifferencebetweenpbandpa?4.Whyintheiostreamlibrarythedesignerdefined“operatorvoid*()”f...[阅读全文]
(2024-01-18 05:41:52)
CANDC++TESTING(BASIC)1.What'sprecedence?What'sassociativity?2.What'slvalue?What'srvalue?Why(x=y)=zisillegalinC?3.What'ssignatureoffunction?What'sdifferenceofsignaturesinCandC++?4.What'soverloadingoffunction?What'smangling?5.WhatarestaticvariableandstaticfunctioninC?Whataretheirscopes?6.What'sdifferencebetweenreferenceandpointer?WhyreferenceisneededinC++?7.Howtoa...[阅读全文]
(2024-01-03 12:02:49)
Whatdomathteacherseat?Squaremeals. Whydidthecalfhatehisschoolpicture?Hiscow-lickwasstickingup. WhattimeofdayAdamwascreated?AlittlebeforeEve. WhatdoyoucallaK9whogetslostonHalloween?A“wherewolf(werewolf). Whydidthegranddaughterthinkshelivedinheaven?Becausehergrandmatoldhershewasanangel. Whyisthepianosohardtoopen?Becausethekeysarealreadyinside. Whydokittensknowsomuchaboutchurch?Th...[阅读全文]
(2023-12-17 13:29:56)
有人认为代数几何是很难理解的数学。本文想通俗地介绍它的一些基本概念。在平面上有一单位圆,x^2+y^2=1.设圆上的点的座标为(1/√2,1/√2),(1/√2,-1/√2)。对应在座标轴上可表示如下：这就构成座标环（Ring）。
—---------(-1/√2)-----------------(1/√2)-----------(3/√2)-----
在单位圆上取值的函数f1(x,y)=y－－－[(1/√2,1/√2),(1/√2,-1/√2)]&m...[阅读全文]
