Codeforces 489D Unbearable Controversy of Being

题目链接:http://codeforces.com/problemset/problem/489/D


题意:给出n点,m条有向边,问有多少个如下图的菱形



思路:枚举2点,以及与第一个点的边,若是该边的终点与第二个点相连,则第一个点和第二个点有一条菱形边,算出2点间所有的菱形边则可以求出有多少个菱形,看起来时间复杂度是o(n*n*m)但是用了vecter动态数组,其实就是枚举n个点以及m条边复杂度书o(n*m)


#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#define maxn 3030
using namespace std;

int G[maxn][maxn];
vector <int> link[maxn];


int main()
{
    int n,m;
    while (scanf("%d%d",&n,&m)!=EOF)
    {
        memset(G,0,sizeof(G));
        memset(link,0,sizeof(link));
        for (int i=0;i<m;i++)
        {
            int u,v;
            scanf("%d%d",&u,&v);
            G[u][v]=1;
            link[u].push_back(v);
        }

        int res=0;
        for (int i=1;i<=n;i++)
        {
            for (int j=1;j<=n;j++)
            {
                if (i==j) continue;
                int sum=0;
                for (int k=0;k<link[i].size();k++)
                {
                    int v=link[i][k];
                    if (G[v][j]==1) sum++;
                }
                res+=sum*(sum-1)/2;
            }
        }
        printf("%d\n",res);
    }
}


### Codeforces 1487D Problem Solution The problem described involves determining the maximum amount of a product that can be created from given quantities of ingredients under an idealized production process. For this specific case on Codeforces with problem number 1487D, while direct details about this exact question are not provided here, similar problems often involve resource allocation or limiting reagent type calculations. For instance, when faced with such constraints-based questions where multiple resources contribute to producing one unit of output but at different ratios, finding the bottleneck becomes crucial. In another context related to crafting items using various materials, it was determined that the formula `min(a[0],a[1],a[2]/2,a[3]/7,a[4]/4)` could represent how these limits interact[^1]. However, applying this directly without knowing specifics like what each array element represents in relation to the actual requirements for creating "philosophical stones" as mentioned would require adjustments based upon the precise conditions outlined within 1487D itself. To solve or discuss solutions effectively regarding Codeforces' challenge numbered 1487D: - Carefully read through all aspects presented by the contest organizers. - Identify which ingredient or component acts as the primary constraint towards achieving full capacity utilization. - Implement logic reflecting those relationships accurately; typically involving loops, conditionals, and possibly dynamic programming depending on complexity level required beyond simple minimum value determination across adjusted inputs. ```cpp #include <iostream> #include <vector> using namespace std; int main() { int n; cin >> n; vector<long long> a(n); for(int i=0;i<n;++i){ cin>>a[i]; } // Assuming indices correspond appropriately per problem statement's ratio requirement cout << min({a[0], a[1], a[2]/2LL, a[3]/7LL, a[4]/4LL}) << endl; } ``` --related questions-- 1. How does identifying bottlenecks help optimize algorithms solving constrained optimization problems? 2. What strategies should contestants adopt when translating mathematical formulas into code during competitive coding events? 3. Can you explain why understanding input-output relations is critical before implementing any algorithmic approach? 4. In what ways do prefix-suffix-middle frameworks enhance model training efficiency outside of just tokenization improvements? 5. Why might adjusting sample proportions specifically benefit models designed for tasks requiring both strong linguistic comprehension alongside logical reasoning skills?
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