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 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

---

#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
int n, sq[100010];
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		int t1;
		scanf("%d", &t1);
		sq[t1] = i;
	}
	int cnt = 0;
	for (int i = 1; i < n; i++) {
		if (i != sq[i]) {
			while (sq[0] != 0) {
				swap(sq[0], sq[sq[0]]);
				cnt++;
			}
			if (i != sq[i]) {
				swap(sq[0], sq[i]);
				cnt++;
			}
		}
	}
	printf("%d\n", cnt);
	return 0;
}