[英]How to relocate an element in one array in C++
我回答了这个面试问题，但我失败了，所以我来这里是为了不再失败！
我有一个大小为 16 和 5 < givenIndex < 10 的 int 数组。
我必须将这个索引中的元素打印每个可能的数组（有 16 个），方法是将 givenIndex 处的元素移动到数组中的每个位置并推动其余元素。
例如：
int array[16] = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16};
int givenIndex = 6;
由于array[givenIndex] = 7 ，我需要将 7 移动到每个可能的位置并打印该数组。
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]
[7,1,2,3,4,5,6,8,9,10,11,12,13,14,15,16]
[1,7,2,3,4,5,6,8,9,10,11,12,13,14,15,16]
[1,2,7,3,4,5,6,8,9,10,11,12,13,14,15,16]
这是 16 个案例。
我正在尝试的是：
for(int i = 0;i<16;i++){
array[i] = array[indexInsercion]
if (i<indexInsert){
//right shift
array[i] = array[i+1]
}else if(i == indexInsert){
//no shift
}else{
//left shift
array[i] = array[i-1]
}
}
我能得到一些帮助吗？
我们只能猜测面试官希望看到什么。 如果我是面试官，我希望看到你保持简单。 这是我认为可以在面试情况下从头开始编写的代码：
#include <iostream>
#include <array>
template <size_t size>
void print_replaced(const std::array<int,size>& x,size_t index){
for (int i=0;i<size;++i){
for (int j=0;j<i;++j) {
if (j == index) continue;
std::cout << x[j] << " ";
}
std::cout << x[index] << " ";
for (int j=i;j<size;++j) {
if (j == index) continue;
std::cout << x[j] << " ";
}
std::cout << "\n";
}
}
int main() {
std::array<int,16> x{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16};
print_replaced(x,6);
}
这是解决问题的第一种方法，使用循环打印数组元素的 16 种不同组合。 打印每一行遵循简单的逻辑：我们打印应该替换的元素之前的所有元素，然后是应该打乱的元素，然后是剩余的元素。
这很简单，但错了。 它的输出是：
7 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16
1 7 2 3 4 5 6 8 9 10 11 12 13 14 15 16
1 2 7 3 4 5 6 8 9 10 11 12 13 14 15 16
1 2 3 7 4 5 6 8 9 10 11 12 13 14 15 16
1 2 3 4 7 5 6 8 9 10 11 12 13 14 15 16
1 2 3 4 5 7 6 8 9 10 11 12 13 14 15 16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 4 5 6 8 7 9 10 11 12 13 14 15 16
1 2 3 4 5 6 8 9 7 10 11 12 13 14 15 16
1 2 3 4 5 6 8 9 10 7 11 12 13 14 15 16
1 2 3 4 5 6 8 9 10 11 7 12 13 14 15 16
1 2 3 4 5 6 8 9 10 11 12 7 13 14 15 16
1 2 3 4 5 6 8 9 10 11 12 13 7 14 15 16
1 2 3 4 5 6 8 9 10 11 12 13 14 7 15 16
1 2 3 4 5 6 8 9 10 11 12 13 14 15 7 16
有一行出现了两次，最后一行丢失了。
作为面试官，我不会对第一次尝试没有产生正确输出感到惊讶。 我不在乎那个。 那不是减分。 我会关心的是你对此有何反应。 你知道接下来的步骤吗？ 您是否有修复错误输出的策略？ 或者你只是因为第一次尝试就没有写出正确的代码而感到恐慌？ 这就是我想在面试中检查的内容，然后就是练习的结尾。 我想提出更多不同的问题，而不是给你时间修复所有错误并编写正确且经过测试的代码，因为我知道这比我们在面试中花费的时间更多。
我会让你来修复上面的代码;)
这是一个快速的尝试。 基本上只是跟踪给定索引应该去的位置并在那里打印它以及跳过它的原始位置。
#include <iostream>
int main()
{
int array[16] = { 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 };
int givenIndex = 6;
for (int p = 0; p <= 16; ++p)
{
if (p != givenIndex)
{
std::cout << "[";
for (int i = 0; i < 16; ++i)
{
if (i == p)
{
if (i > 0)
{
std::cout << ",";
}
std::cout << array[givenIndex];
}
if (array[i] != array[givenIndex])
{
if (i > 0 || p == 0)
{
std::cout << ",";
}
std::cout << array[i];
}
}
if (p == 16)
{
std::cout << "," << array[givenIndex];
}
std::cout << "]\n";
}
}
}
输出：
[7,1,2,3,4,5,6,8,9,10,11,12,13,14,15,16]
[1,7,2,3,4,5,6,8,9,10,11,12,13,14,15,16]
[1,2,7,3,4,5,6,8,9,10,11,12,13,14,15,16]
[1,2,3,7,4,5,6,8,9,10,11,12,13,14,15,16]
[1,2,3,4,7,5,6,8,9,10,11,12,13,14,15,16]
[1,2,3,4,5,7,6,8,9,10,11,12,13,14,15,16]
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]
[1,2,3,4,5,6,8,7,9,10,11,12,13,14,15,16]
[1,2,3,4,5,6,8,9,7,10,11,12,13,14,15,16]
[1,2,3,4,5,6,8,9,10,7,11,12,13,14,15,16]
[1,2,3,4,5,6,8,9,10,11,7,12,13,14,15,16]
[1,2,3,4,5,6,8,9,10,11,12,7,13,14,15,16]
[1,2,3,4,5,6,8,9,10,11,12,13,7,14,15,16]
[1,2,3,4,5,6,8,9,10,11,12,13,14,7,15,16]
[1,2,3,4,5,6,8,9,10,11,12,13,14,15,7,16]
[1,2,3,4,5,6,8,9,10,11,12,13,14,15,16,7]
如果期望只是按给定顺序打印数组的元素：
跟踪要打印的数组元素的当前索引，例如indx -
givenIndex处打印元素。indx等于givenIndex跳过它，打印indx + 1元素，否则在打印元件indx和增加indx由1 。执行：
#include <iostream>
#include <array>
int main() {
std::array<int, 16> array = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16};
std::size_t givenIndex = 6;
for (std::size_t i = 0, indx = 0; i < array.size(); indx = 0, ++i) {
std::cout << '[';
for (std::size_t j = 0; j < array.size(); ++j) {
if (j == i) {
std::cout << array[givenIndex] << ',';
continue;
}
if (indx == givenIndex) {
++indx;
}
std::cout << array[indx++] << ',';
}
std::cout << ']';
std::cout << '\n';
}
return 0;
}
输出：
# ./a.out
[7,1,2,3,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,7,2,3,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,7,3,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,7,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,7,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,7,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,7,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,7,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,7,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,7,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,7,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,7,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,14,7,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,14,15,7,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,14,15,16,7,]
如果期望改变数组中元素的顺序，然后打印数组：
首先将givenIndex处的元素移动到数组的第0个索引，然后 -
执行：
#include <iostream>
#include <array>
void print_array (std::array<int, 16>& array) {
std::cout << '[';
for (std::size_t indx = 0; indx < array.size(); ++indx) {
std::cout << array[indx] << ',';
}
std::cout << ']';
std::cout << '\n';
}
void rearrange_array_elem (std::array<int, 16>& array, std::size_t givenIndx) {
// move the element at givneIndx to first position in array
for (std::size_t j = givenIndx; j > 0; --j) {
std::swap (array[j], array[j - 1]);
}
// print array
print_array (array);
for (std::size_t indx = 0; indx < array.size() - 1; ++indx) {
// swap current element with its next element
std::swap (array[indx], array[indx + 1]);
print_array (array);
}
}
int main() {
std::array<int, 16> array = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16};
std::size_t givenIndex = 6;
rearrange_array_elem (array, givenIndex);
return 0;
}
输出：
# ./a.out
[7,1,2,3,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,7,2,3,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,7,3,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,7,4,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,7,5,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,7,6,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,7,9,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,7,10,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,7,11,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,7,12,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,7,13,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,7,14,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,14,7,15,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,14,15,7,16,]
[1,2,3,4,5,6,8,9,10,11,12,13,14,15,16,7,]
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