Next Number with Same Set of Digits

最新推荐文章于 2023-07-15 20:19:14 发布

原创最新推荐文章于 2023-07-15 20:19:14 发布 · 495 阅读

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本文介绍了一个算法，用于找出一个整数的所有可能排列中紧接其后的最小数字。通过交换和反转操作实现，适用于数字处理和排序算法的学习。

Problem: Reorder the digits of a number, in order to get the next number which is the least one that is greater than the input number. For example, the number 34724126 is the next number of 34722641 when reordering digits.

/* Copyleft: Ming Lin <minggr@gmail.com> */

#include <stdio.h>

void reverse(int *data, int n)
{
	int *s, *e;

	s = data;	
	e = data + (n-1);
	while (s < e) {
		int tmp;

		tmp = *s;
		*s = *e;
		*e = tmp;
		s++;
		e--;
	}
}

/*
 * 34722641 -> swap 2 and 4
 * 34724621 -> reverse "621"
 * 34724126
 */
int least_greater_number(int *data, int n)
{
	int tmp;
	int i, j;	

	i = n-1;
	tmp = data[i--];
	while (i >= 0) {
		if (data[i] < tmp)	
			break;
		tmp = data[i--];
	}

	if (i < 0)
		return 0;

	j = n;
	while (j--) {
		if (data[j] > data[i])
			break;
	}

	tmp = data[i];
	data[i] = data[j];
	data[j] = tmp;

	reverse(&data[i+1], n-i-1);

	return 1;
}

void print_data(int *data, int n)
{
	int i;

	for (i = 0; i < n; i++)
		printf("%d", data[i]);
	printf("\n");
}

int main()
{
	int data[] = {3, 4, 7, 2, 2, 6, 4, 1};
	int n = 8;

	print_data(data, n);
	if (least_greater_number(data, n))
		print_data(data, n);

	return 0;
}