10-排序6 Sort with Swap(0, i)

Given any permutation of the numbers {0, 1, 2,…,N−1}, it is easy to sort them in increasing order. But what ifSwap(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 firstNnonnegative integers.

Input Specification:

Each input file contains one test case, which gives a positiveN(≤105) 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

code

# include int data[100010];bool visited[100010];int travCircle(int s){int current = data[s];int cnt = 1;visited[s] = true;while (current != s){visited[current] = true;cnt++;current = data[current];}return cnt;}int main(void){int n;scanf("%d", &n);for (int i = 0; i < n; ++i) visited[i] = false;for (int i = 0; i < n; ++i) scanf("%d", &data[i]);int ans = 0;for (int i = 0; i < n; ++i){if (visited[i]) continue;int tmp = travCircle(i);if (i == 0){if (tmp == 1) ans += 0;else ans += (tmp - 1);}else{if (tmp == 1) ans += 0;else ans += (tmp + 1);}}printf("%d\n", ans);return 0;}