### 【PAT】1067. Sort with Swap(0,*) (25)

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 (<=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:
```10 3 5 7 2 6 4 9 0 8 1
```
Sample Output:

9

```#include <iostream>
#include <vector>

using namespace std;

struct node{
int pos;
int val;
};

int findWrong(int * positions, int begin, int end){
int i = begin;
for(; i<end; i++){
if(positions[i] != i){
return i;
}
}
return 0;
}

int main(int argc, char** argv) {
int n, i, j, val;
scanf("%d",&n);
//vector<int> positions(n);
int *positions = new int[n];
vector<bool> flag(n,false);
for(i=0; i<n; i++){
scanf("%d",&val);
positions[val] = i;
}
int step = 0, pos;
int index;
index = findWrong(positions, 1, n);
while(index != 0) {
pos = positions[0];
if(pos != 0){
//0未归位
positions[0] = positions[pos] ;
positions[pos] = pos;
step++;
}else{
//0归位了
positions[0] = positions[index];
positions[index] = 0;
step++;
}
index = findWrong(positions,index,n);
}
printf("%d\n",step);
return 0;
}

```