PAT(甲级)1067

1067. Sort with Swap(0,*) (25)

时间限制

150 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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 <cstdio>
#include <cstring>
#define SIZE 100005

int a[SIZE];
int aindex[SIZE];

void swap(int &a,int &b)
{
int tmp=a;
a=b;
b=tmp;
}

int main()
{
int N,i,tmp,count=0;
scanf("%d",&N);
memset(a,0,sizeof(int)*SIZE);
memset(aindex,0,sizeof(int)*SIZE);
for(i=0;i<N;i++){
scanf("%d",&tmp);
a[i] = tmp;
aindex[tmp] =i;
}
for(i=0;i<N;i++){
if(a[i] != i){
swap(a[i],a[aindex[i]]);
count++;
}
}
printf("%d\n",count);
return 0;
}