代码实现：

#include<stdio.h>
#include<stdlib.h>
#include<math.h>

typedef struct
{
	int number, cnt;
}diff;

int cmp(const void *a, const void *b)
{
	diff *aa = (diff*)a, *bb = (diff*)b;
	if (aa->number != bb->number)
		return aa->number > bb->number ? -1 : 1;
	else
		return aa->cnt > bb->cnt ? -1 : 1;
}

int main()
{
	int N, *card;
	
	scanf("%d", &N);
	card = (int*)malloc(sizeof(int)*N);
	for (int i = 0; i < N; i++)
	{
		int num;
		scanf("%d", &num);
		card[i] = fabs(num - i - 1);
	}
	diff *array = (diff*)malloc(sizeof(diff)*N);
	for (int i = 0; i < N; i++)
		array[i].cnt = 0;
	for (int i = 0; i < N; i++)
		array[card[i]].cnt++, array[card[i]].number = card[i];
	qsort(array, N, sizeof(diff), cmp);
	for (int i = 0; i < N; i++)
		if (array[i].cnt > 1)
			printf("%d %d\n", array[i].number, array[i].cnt);

	return 0;
}