C ++：基本数组交换

Question

I simply could not understand why the following code does not work. What could be the possible reason that the operation does not work;

#include <iostream>

using namespace std;

void rotateK(int* arr, int start, int finish) {
    int temp;
    for(int i=0;i<=finish;i++) {
        temp=arr[i];
        arr[i]=arr[finish-i];
        arr[finish-i]=temp;
    }
    for(int i=0;i<=finish;i++)
        cout<<arr[i]<<" ";
    cout<<endl;
}


int main(){
    int arr[5]={1,2,3,4,5};
    rotateK(arr,0,4);
    return 0;

}

Answer 1

It does work (although not how you want it to work). But swaps the elements twice , that's why the processed array is identical to the original one.

You probably want:

for(int i=0 ; i<=finish/2 ; i++)

or even

for(int i=start;i<=(finish-start)/2 + start;i++)

so that you actually use start .

Answer 2

You're swapping elements twice. You can consider this idea of flipping a segment of an array.

int i = start;
int j = finish;
while( i < j ) {
    temp=arr[i];
    arr[i]=arr[j];
    arr[j]=temp;
    ++i; --j;
}

It's difficult to make a mistake if you write it like this.