javascript：为for循环创建for循环

本文介绍了javascript：为for循环创建for循环的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 我必须解决以下问题： 9个值，从1到9（0和10不被接受）和所有数字需要不同。9 values, from 1 to 9 (0 and 10 not accepted) and all numbers need to be different.为了解决这个问题，我为循环中的循环制作了那些可怕的东西。 （我添加了2个条件来检查我是否有其中一个解决方案） 它有效，但我想知道如何以更好的方式在for循环内创建for循环？To solve the probem, I made those horrible for loops inside for loops.(I added 2 more conditions to check if i had one of the solutions)It is working, but I was wondering how to create those for loops inside for loops in a better way?此外，每个数字都可以'等于另一个。你怎么能比我做到这一点呢？ （同样，可以删除2个第一个条件）Also, each number can't be equal to another. How can you accomplish this another way than I did? (Again, 2 first conditions can be deleted)这是代码：var a = 1, b = 1, c = 1, d = 1, e = 1, f = 1, g = 1, h = 1, i = 1;var x = 0;var result = [];function calc(){ x = a + 13 * b / c + d + 12 * e - f - 11 + g * h / i - 10; if(x == 66){ result.push([a, b , c , d , e, f, g, h, i] ); }}for(a = 1; a < 10; a++){ calc(); for(b = 1; b < 10; b++){ calc(); for(c = 1; c < 10; c++){ calc(); for(d = 1; d < 10; d++){ calc(); for(e = 1; e < 10; e++){ calc(); for(f = 1; f < 10; f++){ calc(); for(g = 1; g < 10; g++){ calc(); for(h = 1; h < 10; h++){ calc(); for(i = 1; i < 10; i++){ calc(); } } } } } } } }}console.log(result);var result2 = result.filter(function(el){ return el[0] == 5 && el[1] == 9 && el[0] != el[1] && el[0] != el[2] && el[0] != el[3] && el[0] != el[4] && el[0] != el[5] && el[0] != el[6] && el[0] != el[7] && el[0] != el[8] && el[1] != el[0] && el[1] != el[2] && el[1] != el[3] && el[1] != el[4] && el[1] != el[5] && el[1] != el[6] && el[1] != el[7] && el[1] != el[8] && el[2] != el[0] && el[2] != el[1] && el[2] != el[3] && el[2] != el[4] && el[2] != el[5] && el[2] != el[6] && el[2] != el[7] && el[2] != el[8] && el[3] != el[0] && el[3] != el[1] && el[3] != el[2] && el[3] != el[4] && el[3] != el[5] && el[3] != el[6] && el[3] != el[7] && el[3] != el[8] && el[4] != el[0] && el[4] != el[1] && el[4] != el[2] && el[4] != el[3] && el[4] != el[5] && el[4] != el[6] && el[4] != el[7] && el[4] != el[8] && el[5] != el[0] && el[5] != el[1] && el[5] != el[2] && el[5] != el[3] && el[5] != el[4] && el[5] != el[6] && el[5] != el[7] && el[5] != el[8] && el[6] != el[1] && el[6] != el[2] && el[6] != el[3] && el[6] != el[4] && el[6] != el[5] && el[6] != el[7] && el[6] != el[8] && el[7] != el[0] && el[7] != el[1] && [7] != el[2] && el[7] != el[3] && el[7] != el[4] && el[7] != el[5] && el[7] != el[6] && el[7] != el[8] && el[8] != el[0] && el[8] != el[1] && el[8] != el[2] && el[8] != el[3] && el[8] != el[4] && el[8] != el[5] && el[8] != el[6] && el[8] != el[7];});console.log(result2);推荐答案对于初学者你可以赚 N x嵌套 for 这样的循环for starters you can make N x nested for loops like this C ++中的nested_for nested_for in C++你可以按 9 数字生成来处理您的问题You can handle your problem as a 9 digit number generation由于您的数字没有重复，您可以放弃多次迭代。如果以上述方式编码（如嵌套），你会得到类似的结果：As your digits are not repeating you can discard many iterations. If encoded in the above manner (like nested for) you will came up with something like this: C ++中的广义排列（不重复）：//---------------------------------------------------------------------------//--- permutation class ver 0.00 --------------------------------------------//---------------------------------------------------------------------------#ifndef _permutation_h#define _permutation_h/*--------------------------------------------------------------------------- // usage: permutation per; per.alloc(N); per.first(); for (;;) { ... here per.i[0..N-1] contains actual permutation ... N! permutations if (!per.next()) break; }//-------------------------------------------------------------------------*/class permutation {public: int *i; // i[N] permutation BYTE *a; // a[N] item not used yet ? int N; // items int ix; // actual permutation layer permutation() { N=0; i=NULL; a=NULL; ix=0; } permutation(permutation& b) { *this=b; } ~permutation() { free(); } permutation* operator = (const permutation *b) { *this=*b; return this; } permutation* operator = (const permutation &b) { alloc(b.N); for (int j=0;j<N;j++) { i[j]=b.i[j]; a[j]=b.a[j]; } ix=b.ix; return this; } void alloc(int _N) { free(); i=new int[_N]; if (i==NULL) return; a=new BYTE[_N]; if (a==NULL) { free(); return; } N=_N; } void free () { N=0; ix=0; if (i!=NULL) delete i; i=NULL; if (a!=NULL) delete a; a=NULL; } void first() // init permutation { for (ix=0;ix<N;ix++) { i[ix]=ix; a[ix]=0; } ix--; } bool next() // next permutation return if it is not last { int *ii=&i[ix]; for (;;) { if (*ii>=0) a[*ii]=1; for ((*ii)++;*ii<N;(*ii)++) if (a[*ii]) { a[*ii]=0; break; } if (*ii>=N) { if (ix== 0) return false; *ii=-1; ix--; ii=&i[ix]; } else{ if (ix==N-1) return true; ix++; ii=&i[ix]; } } } };//---------------------------------------------------------------------------#endif//---------------------------------------------------------------------------//---------------------------------------------------------------------------//---------------------------------------------------------------------------重要的东西是 first（）和 next（）成员，每个置换作为索引存储在 i [] 数组中，因此设置 N = 9 ，输出数字将（per.i [0] +1），（per.i [1] +1），...，（per.i [9] 1）The important stuff is in first() and next() members, each permutation is stored in the i[] array as index so set N=9 and your output numbers will be (per.i[0]+1),(per.i[1]+1),...,(per.i[9]+1) 它的工作方式如下： first（）将排列初始化为州 i [9] =（0,1,2，... 8）和 a [9] =（0,0,0，... 0）first() initialize permutation to state i[9]=(0,1,2,...8) and a[9]=(0,0,0,...0)我会这样简单地写这个： i = 012345678，a = 000000000 其中I will write this for simplicity like this: i=012345678,a=000000000 where ix 指向最后一位数 i 是实际的排列 a 标记数字是否未使用（1）或使用（0）（以避免 O（N ^ N）操作）ix points to last digiti is the actual permutationa flags if digit is unused(1) or used(0) (to avoid O(N^N) operation) next（）递增到下一个有效排列next() increment to next valid permutation将最后一位数增加到下一个未使用的值。如果没有未使用的值将其设置为未使用并增加前一个数字。溢出也是如此。第一次迭代将是这样的：Increase the last digit to next unused value. If no unused value set it as unused and increment previous digit. The same goes for overflow. The first iteration will be like this:i=012345678,a=000000000 // starting iterationi=01234567? a=000000001 // unset (no unused values)i=01234568? a=000000010 // increment 8th digiti=012345687 a=000000000 // set the last digit result下一次迭代：i=012345687 a=000000000 // starting iterationi=01234568? a=000000010 // unset (no unused values)i=0123456?? a=000000011 // unset (8->9 overflow)i=0123457?? a=000000101 // increment 7th digiti=01234576? a=000000001 // after overflow digit set to lowest free valuei=012345768 a=000000000 // after overflow digit set to lowest free value我希望它足够清楚。如果你使用的话很粗糙递归而不是迭代，代码看起来会更好，但在大多数语言中，由于堆栈/堆垃圾而运行速度也会变慢Of coarse if you use recursion instead of iteration the code will look much nicer but in most languages will run also slower due to stack/heap trashing正如@NikolaDimitroff指出的那样，这是在 C ++ 而不是javascript所以：As @NikolaDimitroff pointed out this is in C++ instead of javascript so: 忽略 new，delete 和 class 其他成员 first（），next（） set N = 9; 和数组 i，可以是静态的，如： int i [9] ; BYTE a [9];ignore new,delete and class members other then first(),next()set N=9; and arrays i,a can be static like: int i[9]; BYTE a[9]; 此解决方案 O（ N！）用于C ++中的任务：Here the solution O(N!) for the task in C++:int a,b,c,d,e,f,g,h,i;permutation per;per.alloc(9);per.first();for (;;) { if ((per.i[0]+1) +(13*(per.i[1]+1)/(per.i[2]+1))+(per.i[3]+1) +(12*(per.i[4]+1)) -(per.i[5]+1)-11 +((per.i[6]+1)*(per.i[7]+1)/(per.i[8]+1))-10 ==66) { a=per.i[0]+'1'; b=per.i[1]+'1'; c=per.i[2]+'1'; d=per.i[3]+'1'; e=per.i[4]+'1'; f=per.i[5]+'1'; g=per.i[6]+'1'; h=per.i[7]+'1'; i=per.i[8]+'1'; // here a,b,c,d,e,f,g,h,i holds the solution break; } if (!per.next()) break; } 这篇关于javascript：为for循环创建for循环的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！