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  • CodeForces

    /*
    此题最初太过想当然了,非常不好,当初TLE的时候,也没有想想能不能用更好的方法,毕竟排序的效率应该没有查找快,而我...每次都要用memcpy复制页数的顺序,每次都要调用一次sort()函数,应该会产生不小的时间开销
    
    后来发现,真的有简单的思路,而且不止一种
    
    1. 可以找到[l,r]区间对应的位置的数组元素中,页码比x对应的页码小的个数,记作tot,若l+tot==x,则没有变动,否则变动
    2. 也可以分别统计,[l,x]区间对应的位置的数组元素中,页码比x大的,和[x,r]区间对应的位置的数组元素中,页码比x小的个数,若两者相等,则不会变动,否则变动
    
    参考借鉴至网址:
    http://blog.csdn.net/szh_0808/article/details/72793597
    
    再次提醒:
    不要想当然,不要想当然!!!第一时间能想到的方法,往往不是效率最高的
    
    再贴上自己的TLE代码,以防止重蹈覆辙!
    //Time limit exceeded on test 35
    #include <bits/stdc++.h>
    using namespace std;
    const int N = 10005;
    int a[N], b[N];
    
    struct change
    {
    	int l, r, x;
    	
    	int notchanged()
    	{
    		sort(b+l-1, b+r);
    		return (b[x-1] == a[x-1])?1:0;
    	} 
    }c[N];
    istream& operator >> (istream&in, change &d)
    {
    	in >> d.l >> d.r >> d.x;
    	return in;
    }
    
    int main()
    {
    	cin.tie(0);
        cin.sync_with_stdio(false);
    	int n, m;
    	cin >> n >> m;
    		for (int i = 0; i < n; i++)
    		cin >> a[i];
    		for (int i = 0; i < m; i++)
    		{
    			cin >> c[i];
    		}
    		for (int i = 0; i < m; i++)
    		{
    			if (c[i].l == c[i].r || c[i].x < c[i].l || c[i].x > c[i].r)
    			{
    				cout << "Yes" << endl; continue;
    			} 
    			memcpy(b, a, sizeof(int)*n);
    			if (c[i].notchanged()) cout << "Yes" << endl;
    			else cout << "No" << endl;
    		}
    	return 0;
    }
    
    另外注意这句话的理解:
    For every of such sorting Vladik knows number x — what index of page in permutation he should read.
    x表示的是,它是在整个全排列中的第几个,而不是表示在[l,r]中的第几个
    
    */



    #include <bits/stdc++.h>
    using namespace std;
    const int N = 1e4 + 10;
    int a[N];
    struct change
    {
    	int l, r, x;
    	
    	void solve1()
    	{
    		if (l == r)
    		{
    			cout << "Yes" << endl; return;
    		}
    		int s1 = 0, s2 = 0;
    		for (int i = l; i <= x; i++)
    		{
    			if ( a[i] > a[x] ) s1++;
    		}
    		for (int i = x; i <= r; i++)
    		{
    			if ( a[i] < a[x] ) s2++;
    		}
    		if (s1 == s2) cout << "Yes" << endl;
    		else cout << "No" << endl;
    	}
    	
    	void solve2()
    	{
    		if ( l == r )
    		{
    			cout << "Yes" << endl; return;
    		}
    		int s = 0;
    		for (int i = l; i <= r; i++)
    			if ( a[i] < a[x] )
    			s++;
    			
    		if ( s + l == x ) cout << "Yes" << endl;
    		else cout << "No" << endl;
    		
    	}
    }c[N];
    istream& operator >> (istream&in, change &d)
    {
    	in >> d.l >> d.r >> d.x;
    	return in;
    }
    int main()
    {
    	int n, m;
    	while (cin >> n >> m)
    	{
    		for (int i = 1; i <= n; i++) cin >> a[i];
    		
    		for (int i = 1; i <= m; i++) cin >> c[i];
    		
    		for (int i = 1; i <= m; i++) c[i].solve2();
    		
    	}
    	return 0;
    }


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  • 原文地址:https://www.cnblogs.com/mofushaohua/p/7789503.html
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