PAT A1067. Sort with Swap(0,*) (25)
PAT A1067. Sort with Swap(0,*) (25)

PAT A1067. Sort with Swap(0,*) (25)
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https://www.patest.cn/contests/pat-a-practise/1067

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`

## 解题思路

``````#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
vector<int> a, b;
int main() {
int n, t, c = 0;
scanf("%d", &n);
for (int i = 0; i < n; ++i) {
scanf("%d", &t);
a.push_back(t);
}
int cnt = 0;
while (c < n) { //序列排序未结束
if (0 == a[0]) { //首位为0，找出第一个未排序的数的位置
for (; c < n && c == a[c]; ++c)
continue;
if (c >= n) break;
swap(a[0], a[c]);
++cnt;
} else { //首位非0，与应处于的位置交换
swap(a[0], a[a[0]]);
++cnt;
}
}
printf("%d\n", cnt);
return 0;
}``````

http://blog.csdn.net/apie_czx/article/details/48243647

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