iiitv/ChefLib

// made by Divyesh Puri
#include <stdio.h>
int main()    {
    int t;
    scanf("%d", &t);
    while(t--) {
        int n;
        scanf("%d", &n);
        int arr[n + 1];
        int i, j, k, l;
        for(i = 1; i <= n; i++){
            arr[i] = i;
        }
        if (n % 2 == 0)    {
            for(i = 1; i < n; i += 2){
                int temp = arr[i];
                arr[i] = arr[i + 1];
                arr[i + 1] = temp;
            }
        }
        else {
            for(i = 1; i < n; i += 2){
                int temp = arr[i];
                arr[i] = arr[i + 1];
                arr[i + 1] = temp;
            }
            j = arr[n - 1];
            arr[n - 1] = arr[n];
            arr[n] = j;
        }
        for(i = 1; i <= n; i++){
            printf("%d ", arr[i]);
        }
        printf("\n");
    }
}