1067 Sort with Swap(0, i) （25 分）

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 Nnonnegative 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:

103 5 7 2 6 4 9 0 8 1

Sample Output:

9 题意：输入一个序列，如果某个数不在该位置，比如1不在1号位，那么需要和0交换，直到整个序列都在数所对应的位置上，过程中只能用0交换，求最小交换次数 分析：贪心题，要次数最小，只要每次和0交换后到达所对应的位置，简单地说就是换一次就不用再换了。 这里要考虑两种情况，第一种是0不在0号位，那么找到0在的位置，比如在3号位，那么和三号位对应的数交换； 第二种是0在0号位，找到第一个不在本位上的数交换。 为了方便起见，数组用来存数的位置。如下所示：

t	4	1	2	0	3
a[]	3	1	2	4	0

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