Codeforces Round #277.5 (Div. 2)A——SwapSort

A. SwapSort
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
In this problem your goal is to sort an array consisting of n integers in at most n swaps. For the given array find the sequence of swaps that makes the array sorted in the non-descending order. Swaps are performed consecutively, one after another.
Note that in this problem you do not have to minimize the number of swaps — your task is to find any sequence that is no longer than n.
Input
The first line of the input contains integer n (1 ≤ n ≤ 3000) — the number of array elements. The second line contains elements of array: a0, a1, ..., an - 1 ( - 109 ≤ ai ≤ 109), where ai is the i-th element of the array. The elements are numerated from 0 to n - 1 from left to right. Some integers may appear in the array more than once.
Output
In the first line print k (0 ≤ k ≤ n) — the number of swaps. Next k lines must contain the descriptions of the k swaps, one per line. Each swap should be printed as a pair of integers i, j (0 ≤ i, j ≤ n - 1), representing the swap of elements ai and aj. You can print indices in the pairs in any order. The swaps are performed in the order they appear in the output, from the first to the last. It is allowed to print i = j and swap the same pair of elements multiple times.
If there are multiple answers, print any of them. It is guaranteed that at least one answer exists.
Sample test(s)
Input

5
5 2 5 1 4

Output

2
0 3
4 2

Input

6
10 20 20 40 60 60

Output

0

Input

2
101 100

Output

1
0 1

순서를 정하고 순서 전과 비교하면 다르게 이 자리에 있어야 할 수를 뒤로 찾아서 교환한다

#include <map>
#include <set>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

int a[3030];
int b[3030];

struct node
{
	int x, y;
}pp[3030];

int main()
{
	int n;
	while (~scanf("%d", &n))
	{
		int cnt = 0;
		for (int i = 0; i < n; ++i)
		{
			scanf("%d", &a[i]);
			b[i] = a[i];
		}
		sort(b, b + n);
		int x, y;
		for (int i = 0; i < n; ++i)
		{
			if (a[i] == b[i])
			{
				continue;
			}
			x = i;
			for (int j = i + 1; j < n; ++j)
			{
				if (a[j] == b[i])
				{
					y = j;
					break;
				}
			}
			++cnt;
			pp[cnt].x = x;
			pp[cnt].y = y;
			a[x] ^= a[y];
			a[y] ^= a[x];
			a[x] ^= a[y];
		}
		printf("%d
", cnt);
		for (int i = 1; i <= cnt; ++i)
		{
			printf("%d %d
", pp[i].x, pp[i].y);
		}
	}
	return 0;
}