问题

Given any permutation of the numbers {0, 1, 2,…, N−1}, it is easy to sort them in increasing order. But what if Swap(0, *) is the ONLY operation that is allowed to use? For example, to sort {4, 0, 2, 1, 3} we may apply the swap operations in the following way:

Swap(0, 1) => {4, 1, 2, 0, 3}
Swap(0, 3) => {4, 1, 2, 3, 0}
Swap(0, 4) => {0, 1, 2, 3, 4}

Now you are asked to find the minimum number of swaps need to sort the given permutation of the first N nonnegative integers.
Input Specification:

Each input file contains one test case, which gives a positive N (≤10​5​​) followed by a permutation sequence of {0, 1, …, N−1}. All the numbers in a line are separated by a space.
Output Specification:

For each case, simply print in a line the minimum number of swaps need to sort the given permutation.
Sample Input:

10
3 5 7 2 6 4 9 0 8 1

Sample Output:

9

解决方法

分析：贪心算法

#include<iostream>
using namespace std;
int main()
{
	int n, t, cnt = 0, a[100010];
	scanf("%d", &n);
	for (int i = 0; i < n; i++)
	{
		scanf("%d", &t);
		a[i] = t;
	}
	for (int i = 0; i < n; i++)
	{
		if (i != a[i])
		{
			while (a[0] != 0)
			{
				swap(a[0], a[a[0]]);
				cnt++;
			}
		}
		if (i != a[i])
		{
			swap(a[0], a[i]);
			cnt++;
		}
	}
	printf("%d", cnt);
	return 0;
}