两个数相同也行。
a ^= b 之后，a 就变 0 了，b ^= a 之后， b 还是原来的那个数，再 a ^= b，a 也还是原来的数。

没想到 小z 还被忽悠了。不应该怀疑这个古老手法的正确性呀。

最近发奋阅读汇编代码。 XOR用来清零或者是基本的加解密数据。

与这个类似，很多人也以为a++是不用临时变量的。我曾经说过这种误区，以为写的代码短、量少，就是精辟的程序，其实不然。一个很著名的测试：给20个元素的数组赋值，用循环和写20行赋值语句，你猜哪个快？

自己写20个赋值语句，不同的人不同的速度 哈哈

所以有数组初始化这个语法，方便手慢的人用哈。

我是快手流

a[0] = 0;
a[1] = 0;
a[2] = 0;
a[3] = 0;
a[4] = 0;
a[5] = 0;
a[6] = 0;
a[7] = 0;
a[8] = 0;
a[9] = 0;
a[10] = 0;
a[11] = 0;
a[12] = 0;
a[13] = 0;
a[14] = 0;
a[15] = 0;
a[16] = 0;
a[17] = 0;
a[18] = 0;
a[19] = 0;
a[20] = 0;
a[21] = 0;
a[22] = 0;
a[23] = 0;
a[24] = 0;
a[25] = 0;
a[26] = 0;
a[27] = 0;
a[28] = 0;
a[29] = 0;
a[30] = 0;
a[31] = 0;
a[32] = 0;
a[33] = 0;
a[34] = 0;
a[35] = 0;
a[36] = 0;
a[37] = 0;
a[38] = 0;
a[39] = 0;
a[40] = 0;
a[41] = 0;
a[42] = 0;
a[43] = 0;
a[44] = 0;
a[45] = 0;
a[46] = 0;
a[47] = 0;
a[48] = 0;
a[49] = 0;
a[50] = 0;
a[51] = 0;
a[52] = 0;
a[53] = 0;
a[54] = 0;
a[55] = 0;
a[56] = 0;
a[57] = 0;
a[58] = 0;
a[59] = 0;
a[60] = 0;
a[61] = 0;
a[62] = 0;
a[63] = 0;
a[64] = 0;
a[65] = 0;
a[66] = 0;
a[67] = 0;
a[68] = 0;
a[69] = 0;
a[70] = 0;
a[71] = 0;
a[72] = 0;
a[73] = 0;
a[74] = 0;
a[75] = 0;
a[76] = 0;
a[77] = 0;
a[78] = 0;
a[79] = 0;
a[80] = 0;
a[81] = 0;
a[82] = 0;
a[83] = 0;
a[84] = 0;
a[85] = 0;
a[86] = 0;
a[87] = 0;
a[88] = 0;
a[89] = 0;
a[90] = 0;
a[91] = 0;
a[92] = 0;
a[93] = 0;
a[94] = 0;
a[95] = 0;
a[96] = 0;
a[97] = 0;
a[98] = 0;
a[99] = 0;
a[100] = 0;
a[101] = 0;
a[102] = 0;
a[103] = 0;
a[104] = 0;
a[105] = 0;
a[106] = 0;
a[107] = 0;
a[108] = 0;
a[109] = 0;
a[110] = 0;
a[111] = 0;
a[112] = 0;
a[113] = 0;
a[114] = 0;
a[115] = 0;
a[116] = 0;
a[117] = 0;
a[118] = 0;
a[119] = 0;
a[120] = 0;
a[121] = 0;
a[122] = 0;
a[123] = 0;
a[124] = 0;
a[125] = 0;
a[126] = 0;
a[127] = 0;
a[128] = 0;
a[129] = 0;
a[130] = 0;
a[131] = 0;
a[132] = 0;
a[133] = 0;
a[134] = 0;
a[135] = 0;
a[136] = 0;
a[137] = 0;
a[138] = 0;
a[139] = 0;
a[140] = 0;
a[141] = 0;
a[142] = 0;
a[143] = 0;
a[144] = 0;
a[145] = 0;
a[146] = 0;
a[147] = 0;
a[148] = 0;
a[149] = 0;
a[150] = 0;
a[151] = 0;
a[152] = 0;
a[153] = 0;
a[154] = 0;
a[155] = 0;
a[156] = 0;
a[157] = 0;
a[158] = 0;
a[159] = 0;
a[160] = 0;
a[161] = 0;
a[162] = 0;
a[163] = 0;
a[164] = 0;
a[165] = 0;
a[166] = 0;
a[167] = 0;
a[168] = 0;
a[169] = 0;
a[170] = 0;
a[171] = 0;
a[172] = 0;
a[173] = 0;
a[174] = 0;
a[175] = 0;
a[176] = 0;
a[177] = 0;
a[178] = 0;
a[179] = 0;
a[180] = 0;
a[181] = 0;
a[182] = 0;
a[183] = 0;
a[184] = 0;
a[185] = 0;
a[186] = 0;
a[187] = 0;
a[188] = 0;
a[189] = 0;
a[190] = 0;
a[191] = 0;
a[192] = 0;
a[193] = 0;
a[194] = 0;
a[195] = 0;
a[196] = 0;
a[197] = 0;
a[198] = 0;
a[199] = 0;
a[200] = 0;
a[201] = 0;
a[202] = 0;
a[203] = 0;
a[204] = 0;
a[205] = 0;
a[206] = 0;
a[207] = 0;
a[208] = 0;
a[209] = 0;
a[210] = 0;
a[211] = 0;
a[212] = 0;
a[213] = 0;
a[214] = 0;
a[215] = 0;
a[216] = 0;
a[217] = 0;
a[218] = 0;
a[219] = 0;
a[220] = 0;
a[221] = 0;
a[222] = 0;
a[223] = 0;
a[224] = 0;
a[225] = 0;
a[226] = 0;
a[227] = 0;
a[228] = 0;
a[229] = 0;
a[230] = 0;
a[231] = 0;
a[232] = 0;
a[233] = 0;
a[234] = 0;
a[235] = 0;
a[236] = 0;
a[237] = 0;
a[238] = 0;
a[239] = 0;
a[240] = 0;
a[241] = 0;
a[242] = 0;
a[243] = 0;
a[244] = 0;
a[245] = 0;
a[246] = 0;
a[247] = 0;
a[248] = 0;
a[249] = 0;
a[250] = 0;
a[251] = 0;
a[252] = 0;
a[253] = 0;
a[254] = 0;
a[255] = 0;
a[256] = 0;
a[257] = 0;
a[258] = 0;
a[259] = 0;
a[260] = 0;
a[261] = 0;
a[262] = 0;
a[263] = 0;
a[264] = 0;
a[265] = 0;
a[266] = 0;
a[267] = 0;
a[268] = 0;
a[269] = 0;
a[270] = 0;
a[271] = 0;
a[272] = 0;
a[273] = 0;
a[274] = 0;
a[275] = 0;
a[276] = 0;
a[277] = 0;
a[278] = 0;
a[279] = 0;
a[280] = 0;
a[281] = 0;
a[282] = 0;
a[283] = 0;
a[284] = 0;
a[285] = 0;
a[286] = 0;
a[287] = 0;
a[288] = 0;
a[289] = 0;
a[290] = 0;
a[291] = 0;
a[292] = 0;
a[293] = 0;
a[294] = 0;
a[295] = 0;
a[296] = 0;
a[297] = 0;
a[298] = 0;
a[299] = 0;
a[300] = 0;
a[301] = 0;
a[302] = 0;
a[303] = 0;
a[304] = 0;
a[305] = 0;
a[306] = 0;
a[307] = 0;
a[308] = 0;
a[309] = 0;
a[310] = 0;
a[311] = 0;
a[312] = 0;
a[313] = 0;
a[314] = 0;
a[315] = 0;
a[316] = 0;
a[317] = 0;
a[318] = 0;
a[319] = 0;
a[320] = 0;
a[321] = 0;
a[322] = 0;
a[323] = 0;
a[324] = 0;
a[325] = 0;
a[326] = 0;
a[327] = 0;
a[328] = 0;
a[329] = 0;
a[330] = 0;
a[331] = 0;
a[332] = 0;
a[333] = 0;
a[334] = 0;
a[335] = 0;
a[336] = 0;
a[337] = 0;
a[338] = 0;
a[339] = 0;
a[340] = 0;
a[341] = 0;
a[342] = 0;
a[343] = 0;
a[344] = 0;
a[345] = 0;
a[346] = 0;
a[347] = 0;
a[348] = 0;
a[349] = 0;
a[350] = 0;
a[351] = 0;
a[352] = 0;
a[353] = 0;
a[354] = 0;
a[355] = 0;
a[356] = 0;
a[357] = 0;
a[358] = 0;
a[359] = 0;
a[360] = 0;
a[361] = 0;
a[362] = 0;
a[363] = 0;
a[364] = 0;
a[365] = 0;
a[366] = 0;
a[367] = 0;
a[368] = 0;
a[369] = 0;
a[370] = 0;
a[371] = 0;
a[372] = 0;
a[373] = 0;
a[374] = 0;
a[375] = 0;
a[376] = 0;
a[377] = 0;
a[378] = 0;
a[379] = 0;
a[380] = 0;
a[381] = 0;
a[382] = 0;
a[383] = 0;
a[384] = 0;
a[385] = 0;
a[386] = 0;
a[387] = 0;
a[388] = 0;
a[389] = 0;
a[390] = 0;
a[391] = 0;
a[392] = 0;
a[393] = 0;
a[394] = 0;
a[395] = 0;
a[396] = 0;
a[397] = 0;
a[398] = 0;
a[399] = 0;
a[400] = 0;
a[401] = 0;
a[402] = 0;
a[403] = 0;
a[404] = 0;
a[405] = 0;
a[406] = 0;
a[407] = 0;
a[408] = 0;
a[409] = 0;
a[410] = 0;
a[411] = 0;
a[412] = 0;
a[413] = 0;
a[414] = 0;
a[415] = 0;
a[416] = 0;
a[417] = 0;
a[418] = 0;
a[419] = 0;
a[420] = 0;
a[421] = 0;
a[422] = 0;
a[423] = 0;
a[424] = 0;
a[425] = 0;
a[426] = 0;
a[427] = 0;
a[428] = 0;
a[429] = 0;
a[430] = 0;
a[431] = 0;
a[432] = 0;
a[433] = 0;
a[434] = 0;
a[435] = 0;
a[436] = 0;
a[437] = 0;
a[438] = 0;
a[439] = 0;
a[440] = 0;
a[441] = 0;
a[442] = 0;
a[443] = 0;
a[444] = 0;
a[445] = 0;
a[446] = 0;
a[447] = 0;
a[448] = 0;
a[449] = 0;
a[450] = 0;
a[451] = 0;
a[452] = 0;
a[453] = 0;
a[454] = 0;
a[455] = 0;
a[456] = 0;
a[457] = 0;
a[458] = 0;
a[459] = 0;
a[460] = 0;
a[461] = 0;
a[462] = 0;
a[463] = 0;
a[464] = 0;
a[465] = 0;
a[466] = 0;
a[467] = 0;
a[468] = 0;
a[469] = 0;
a[470] = 0;
a[471] = 0;
a[472] = 0;
a[473] = 0;
a[474] = 0;
a[475] = 0;
a[476] = 0;
a[477] = 0;
a[478] = 0;
a[479] = 0;
a[480] = 0;
a[481] = 0;
a[482] = 0;
a[483] = 0;
a[484] = 0;
a[485] = 0;
a[486] = 0;
a[487] = 0;
a[488] = 0;
a[489] = 0;
a[490] = 0;
a[491] = 0;
a[492] = 0;
a[493] = 0;
a[494] = 0;
a[495] = 0;
a[496] = 0;
a[497] = 0;
a[498] = 0;
a[499] = 0;
a[500] = 0;
a[501] = 0;
a[502] = 0;
a[503] = 0;
a[504] = 0;
a[505] = 0;
a[506] = 0;
a[507] = 0;
a[508] = 0;
a[509] = 0;
a[510] = 0;
a[511] = 0;
a[512] = 0;
a[513] = 0;
a[514] = 0;
a[515] = 0;
a[516] = 0;
a[517] = 0;
a[518] = 0;
a[519] = 0;
a[520] = 0;
a[521] = 0;
a[522] = 0;
a[523] = 0;
a[524] = 0;
a[525] = 0;
a[526] = 0;
a[527] = 0;
a[528] = 0;
a[529] = 0;
a[530] = 0;
a[531] = 0;
a[532] = 0;
a[533] = 0;
a[534] = 0;
a[535] = 0;
a[536] = 0;
a[537] = 0;
a[538] = 0;
a[539] = 0;
a[540] = 0;
a[541] = 0;
a[542] = 0;
a[543] = 0;
a[544] = 0;
a[545] = 0;
a[546] = 0;
a[547] = 0;
a[548] = 0;
a[549] = 0;
a[550] = 0;
a[551] = 0;
a[552] = 0;
a[553] = 0;
a[554] = 0;
a[555] = 0;
a[556] = 0;
a[557] = 0;
a[558] = 0;
a[559] = 0;
a[560] = 0;
a[561] = 0;
a[562] = 0;
a[563] = 0;
a[564] = 0;
a[565] = 0;
a[566] = 0;
a[567] = 0;
a[568] = 0;
a[569] = 0;
a[570] = 0;
a[571] = 0;
a[572] = 0;
a[573] = 0;
a[574] = 0;
a[575] = 0;
a[576] = 0;
a[577] = 0;
a[578] = 0;
a[579] = 0;
a[580] = 0;
a[581] = 0;
a[582] = 0;
a[583] = 0;
a[584] = 0;
a[585] = 0;
a[586] = 0;
a[587] = 0;
a[588] = 0;
a[589] = 0;
a[590] = 0;
a[591] = 0;
a[592] = 0;
a[593] = 0;
a[594] = 0;
a[595] = 0;
a[596] = 0;
a[597] = 0;
a[598] = 0;
a[599] = 0;
a[600] = 0;
a[601] = 0;
a[602] = 0;
a[603] = 0;
a[604] = 0;
a[605] = 0;
a[606] = 0;
a[607] = 0;
a[608] = 0;
a[609] = 0;
a[610] = 0;
a[611] = 0;
a[612] = 0;
a[613] = 0;
a[614] = 0;
a[615] = 0;
a[616] = 0;
a[617] = 0;
a[618] = 0;
a[619] = 0;
a[620] = 0;
a[621] = 0;
a[622] = 0;
a[623] = 0;
a[624] = 0;
a[625] = 0;
a[626] = 0;
a[627] = 0;
a[628] = 0;
a[629] = 0;
a[630] = 0;
a[631] = 0;
a[632] = 0;
a[633] = 0;
a[634] = 0;
a[635] = 0;
a[636] = 0;
a[637] = 0;
a[638] = 0;
a[639] = 0;
a[640] = 0;
a[641] = 0;
a[642] = 0;
a[643] = 0;
a[644] = 0;
a[645] = 0;
a[646] = 0;
a[647] = 0;
a[648] = 0;
a[649] = 0;
a[650] = 0;
a[651] = 0;
a[652] = 0;
a[653] = 0;
a[654] = 0;
a[655] = 0;
a[656] = 0;
a[657] = 0;
a[658] = 0;
a[659] = 0;
a[660] = 0;
a[661] = 0;
a[662] = 0;
a[663] = 0;
a[664] = 0;
a[665] = 0;
a[666] = 0;
a[667] = 0;
a[668] = 0;
a[669] = 0;
a[670] = 0;
a[671] = 0;
a[672] = 0;
a[673] = 0;
a[674] = 0;
a[675] = 0;
a[676] = 0;
a[677] = 0;
a[678] = 0;
a[679] = 0;
a[680] = 0;
a[681] = 0;
a[682] = 0;
a[683] = 0;
a[684] = 0;
a[685] = 0;
a[686] = 0;
a[687] = 0;
a[688] = 0;
a[689] = 0;
a[690] = 0;
a[691] = 0;
a[692] = 0;
a[693] = 0;
a[694] = 0;
a[695] = 0;
a[696] = 0;
a[697] = 0;
a[698] = 0;
a[699] = 0;
a[700] = 0;
a[701] = 0;
a[702] = 0;
a[703] = 0;
a[704] = 0;
a[705] = 0;
a[706] = 0;
a[707] = 0;
a[708] = 0;
a[709] = 0;
a[710] = 0;
a[711] = 0;
a[712] = 0;
a[713] = 0;
a[714] = 0;
a[715] = 0;
a[716] = 0;
a[717] = 0;
a[718] = 0;
a[719] = 0;
a[720] = 0;
a[721] = 0;
a[722] = 0;
a[723] = 0;
a[724] = 0;
a[725] = 0;
a[726] = 0;
a[727] = 0;
a[728] = 0;
a[729] = 0;
a[730] = 0;
a[731] = 0;
a[732] = 0;
a[733] = 0;
a[734] = 0;
a[735] = 0;
a[736] = 0;
a[737] = 0;
a[738] = 0;
a[739] = 0;
a[740] = 0;
a[741] = 0;
a[742] = 0;
a[743] = 0;
a[744] = 0;
a[745] = 0;
a[746] = 0;
a[747] = 0;
a[748] = 0;
a[749] = 0;
a[750] = 0;
a[751] = 0;
a[752] = 0;
a[753] = 0;
a[754] = 0;
a[755] = 0;
a[756] = 0;
a[757] = 0;
a[758] = 0;
a[759] = 0;
a[760] = 0;
a[761] = 0;
a[762] = 0;
a[763] = 0;
a[764] = 0;
a[765] = 0;
a[766] = 0;
a[767] = 0;
a[768] = 0;
a[769] = 0;
a[770] = 0;
a[771] = 0;
a[772] = 0;
a[773] = 0;
a[774] = 0;
a[775] = 0;
a[776] = 0;
a[777] = 0;
a[778] = 0;
a[779] = 0;
a[780] = 0;
a[781] = 0;
a[782] = 0;
a[783] = 0;
a[784] = 0;
a[785] = 0;
a[786] = 0;
a[787] = 0;
a[788] = 0;
a[789] = 0;
a[790] = 0;
a[791] = 0;
a[792] = 0;
a[793] = 0;
a[794] = 0;
a[795] = 0;
a[796] = 0;
a[797] = 0;
a[798] = 0;
a[799] = 0;
a[800] = 0;
a[801] = 0;
a[802] = 0;
a[803] = 0;
a[804] = 0;
a[805] = 0;
a[806] = 0;
a[807] = 0;
a[808] = 0;
a[809] = 0;
a[810] = 0;
a[811] = 0;
a[812] = 0;
a[813] = 0;
a[814] = 0;
a[815] = 0;
a[816] = 0;
a[817] = 0;
a[818] = 0;
a[819] = 0;
a[820] = 0;
a[821] = 0;
a[822] = 0;
a[823] = 0;
a[824] = 0;
a[825] = 0;
a[826] = 0;
a[827] = 0;
a[828] = 0;
a[829] = 0;
a[830] = 0;
a[831] = 0;
a[832] = 0;
a[833] = 0;
a[834] = 0;
a[835] = 0;
a[836] = 0;
a[837] = 0;
a[838] = 0;
a[839] = 0;
a[840] = 0;
a[841] = 0;
a[842] = 0;
a[843] = 0;
a[844] = 0;
a[845] = 0;
a[846] = 0;
a[847] = 0;
a[848] = 0;
a[849] = 0;
a[850] = 0;
a[851] = 0;
a[852] = 0;
a[853] = 0;
a[854] = 0;
a[855] = 0;
a[856] = 0;
a[857] = 0;
a[858] = 0;
a[859] = 0;
a[860] = 0;
a[861] = 0;
a[862] = 0;
a[863] = 0;
a[864] = 0;
a[865] = 0;
a[866] = 0;
a[867] = 0;
a[868] = 0;
a[869] = 0;
a[870] = 0;
a[871] = 0;
a[872] = 0;
a[873] = 0;
a[874] = 0;
a[875] = 0;
a[876] = 0;
a[877] = 0;
a[878] = 0;
a[879] = 0;
a[880] = 0;
a[881] = 0;
a[882] = 0;
a[883] = 0;
a[884] = 0;
a[885] = 0;
a[886] = 0;
a[887] = 0;
a[888] = 0;
a[889] = 0;
a[890] = 0;
a[891] = 0;
a[892] = 0;
a[893] = 0;
a[894] = 0;
a[895] = 0;
a[896] = 0;
a[897] = 0;
a[898] = 0;
a[899] = 0;
a[900] = 0;
a[901] = 0;
a[902] = 0;
a[903] = 0;
a[904] = 0;
a[905] = 0;
a[906] = 0;
a[907] = 0;
a[908] = 0;
a[909] = 0;
a[910] = 0;
a[911] = 0;
a[912] = 0;
a[913] = 0;
a[914] = 0;
a[915] = 0;
a[916] = 0;
a[917] = 0;
a[918] = 0;
a[919] = 0;
a[920] = 0;
a[921] = 0;
a[922] = 0;
a[923] = 0;
a[924] = 0;
a[925] = 0;
a[926] = 0;
a[927] = 0;
a[928] = 0;
a[929] = 0;
a[930] = 0;
a[931] = 0;
a[932] = 0;
a[933] = 0;
a[934] = 0;
a[935] = 0;
a[936] = 0;
a[937] = 0;
a[938] = 0;
a[939] = 0;
a[940] = 0;
a[941] = 0;
a[942] = 0;
a[943] = 0;
a[944] = 0;
a[945] = 0;
a[946] = 0;
a[947] = 0;
a[948] = 0;
a[949] = 0;
a[950] = 0;
a[951] = 0;
a[952] = 0;
a[953] = 0;
a[954] = 0;
a[955] = 0;
a[956] = 0;
a[957] = 0;
a[958] = 0;
a[959] = 0;
a[960] = 0;
a[961] = 0;
a[962] = 0;
a[963] = 0;
a[964] = 0;
a[965] = 0;
a[966] = 0;
a[967] = 0;
a[968] = 0;
a[969] = 0;
a[970] = 0;
a[971] = 0;
a[972] = 0;
a[973] = 0;
a[974] = 0;
a[975] = 0;
a[976] = 0;
a[977] = 0;
a[978] = 0;
a[979] = 0;
a[980] = 0;
a[981] = 0;
a[982] = 0;
a[983] = 0;
a[984] = 0;
a[985] = 0;
a[986] = 0;
a[987] = 0;
a[988] = 0;
a[989] = 0;
a[990] = 0;
a[991] = 0;
a[992] = 0;
a[993] = 0;
a[994] = 0;
a[995] = 0;
a[996] = 0;
a[997] = 0;
a[998] = 0;
a[999] = 0;

说的是执行效率，都什么脑子看成书写效率。

汗了 果然快手 四大名捕之一？

你说俺们看 两厢情愿~~