C++ 解法, 执行用时: 14ms, 内存消耗: 2080KB, 提交时间: 2020-08-27

#include<bits/stdc++.h>

using namespace std;

int main()
{
	std::ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    int a[n];
	for(int i=0; i<n; i++) cin >> a[i];
	int i = 0, p = 0;
	for( ;i<n; i++) {
		if(a[i] != i+1) {
			p = i;
			break;
		}
	}
	if(i==n) {
		int t = a[n-1];
		a[n-1] = a[n-2];
		a[n-2] = t;
	} else {
		for(;i<n; i++) {
			if(a[i] == p+1) {
				int t = a[i];
				a[i] = a[p];
				a[p] = t;
				break;
			}
		}
	}
	for(int i=0; i<n; i++) {
		cout << a[i] << " ";
	}
	cout << endl;
    
	return 0;
}

C 解法, 执行用时: 16ms, 内存消耗: 1712KB, 提交时间: 2021-09-17

#include<stdio.h>

int main()
{
    long n = 0;
    long i=1,j=0,tt=0,ttt=0,p=0,q=0;
    int flag = 0;
    while(scanf("%ld",&n) != EOF)
    {
        long *a = (long*)malloc(sizeof(long)*n);
        scanf("%ld",&a[0]);
        for(i=1;i<n;i++)
        {
            scanf("%ld",&a[i]);
            if(a[0] != 1)
            {
                if(a[i] == 1)
                {
                    j = i;
                }
            }
            else
            {
                if(flag==0 && (a[i] != (a[i-1]+1)))
                {
                    p=i;
                    flag = 1;
                    ttt = a[i];
                    tt = (a[i-1]+1);
                    
                }
                else if(flag==1 && a[i] == tt)
                {
                    q=i;
                }
            }
        }
        if(a[0] != 1)
        {
            a[j] = a[0];
            a[0] = 1;
        }
        else if(a[0] == 1 && flag != 0)
        {
            a[p] = tt;
            a[q] = ttt;
        }
        else
        {
            long temp = a[n-1];
            a[n-1] = a[n-2];
            a[n-2] = temp;
        }
        for(long k=0;k<n;k++)
        {
            if(k == (n-1))
            printf("%ld\n",a[k]);
            else
            printf("%ld ",a[k]);
        }
    }
}