Code forces Round #510 div2

最新推荐文章于 2025-01-13 09:41:03 发布

Below_Crusder

最新推荐文章于 2025-01-13 09:41:03 发布

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文章标签： codeforces acm

本文链接：https://blog.youkuaiyun.com/Below_Crusder/article/details/51836240

本文解析了四道经典编程题目，包括画图算法、深度优先搜索、拓扑排序及动态规划等，通过实际代码展示了算法的具体实现过程。

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A 水题：画图

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
#include <string>
using namespace std;

int main()
{
    int n, m;
    char s1[55], s2[55], s3[55];
    cin>>n>>m;
    for(int i = 0; i < m; i++)
    {
        s1[i] = '#';
        s2[i] = '.';
        s3[i] = '.';
        if(!i)
            s2[i] = '#';
        if(i == m - 1)
            s3[i] = '#';
    }
    s1[m] = 0;
    s2[m] = 0;
    s3[m] = 0;
    int cnt = 1, leap = 1;
    while(1)
    {
        if(cnt > n) break;
        if(cnt & 1){
            cout<<s1<<endl;
        }
        else if(leap){
            cout<<s3<<endl;
            leap = 0;
        }
        else{
            cout<<s2<<endl;
            leap = 1;
        }
        cnt++;
    }
    return 0;
}

B :dfs即可

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
#include <string>
using namespace std;
int dx, dy;
int n, m;
int dir[4][2] = {0, 1, 0, -1, 1, 0, -1, 0};
int vis[55][55];
char ss[55][55];
int mark[55][55];
bool isin(int x, int y)
{
    if(x >= 0 && x < n && y >= 0 && y < m)
        return true;
    return false;
}
int dfs(int x, int y, int z)
{
    vis[x][y] = 1;
    for(int i = 0; i < 4; i++)
    {
        int nx = x + dir[i][0];
        int ny = y + dir[i][1];
        if(nx == dx && ny == dy && z >= 3)
            return 1;
        if(isin(nx, ny) && !vis[nx][ny] && ss[nx][ny] == ss[x][y])
        {
            if(!mark[nx][ny]) continue;
            if(dfs(nx, ny, z + 1)) return 1;
            else mark[nx][ny] = 0;
        }
        
    }
    return 0;
}
int main()
{
    cin>>n>>m;
    for(int i = 0; i < n; i++)
        for(int j = 0; j < m; j++)
            cin>>ss[i][j];
    memset(mark, -1, sizeof mark);
    for(int i = 0; i < n; i++)
        for(int j = 0; j < m; j++)
        {
            memset(vis, 0, sizeof(vis));
            memset(mark, -1, sizeof mark);
            dx = i, dy = j;
            if(dfs(i, j, 1)){
                cout<<"Yes"<<endl;
                return 0;
            }
        }
    cout<<"No"<<endl;
    return 0;
}

C：相邻的字符串建图，然后拓扑排序即可

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
#include <string>
using namespace std;
char ss[105][105];
int as[30][30];
int id[30];
char ans[30];
void init()
{
    memset(as, 0, sizeof as);
    memset(id, 0, sizeof id);
}
int topu_sort()
{
    int cnt = 0;
    queue<int> que;
    while(!que.empty())
        que.pop();
    for(int i = 0; i < 26; i++)
    {
        if(!id[i])
            que.push(i);
    }
    while(!que.empty())
    {
        int now = que.front();
        que.pop();
        ans[cnt++] = now + 'a';
        for(int i = 0; i < 26; i++)
        {
            if(as[now][i])
            {
                id[i]--;
                if(id[i] == 0)
                    que.push(i);
            }
        }
    }
    ans[26] = 0;
    if(cnt < 26)
        return 0;
    return 1;
}
int main()
{
    int t;
    cin>>t;
    for(int i = 0; i < t; i++)
        cin>>ss[i];
    init();
    for(int i = 0; i < t - 1; i++)
    {
        
        int len1 = strlen(ss[i]), len2 = strlen(ss[i + 1]), p = 0;
        while(p < min(len1, len2) && ss[i][p] == ss[i + 1][p]) p++;
        if(p == len1 && len1 <= len2) continue;
        if(p == len2 && len2 < len1){
            cout<<"Impossible"<<endl;
            return 0;
        }
        if(as[ss[i][p] - 'a'][ss[i + 1][p] - 'a'])
            continue;
        as[ss[i][p] - 'a'][ss[i + 1][p] - 'a'] = 1;
        id[ss[i + 1][p] - 'a']++;
    }
    
    if(topu_sort())
        cout<<ans<<endl;
    else
        cout<<"Impossible"<<endl;
    return 0;
}

D：利用map动态规划注意输入有重边需更新

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
#include <string>
#include <map>
using namespace std;

int gcd(int a, int b)
{
    if(b == 0) return a;
    return gcd(b, a % b);
}
int main()
{
    int n;
    cin>>n;
    int a[305];
    long long b[305];
    for(int i = 0; i < n; i++)
    {
        cin>>a[i];
    }
    for(int i = 0; i < n; i++)
    {
        cin>>b[i];
    }
    map<int, long long int> std;
    
    for(int i = 0; i < n; i++)
    {
        if(std.count(a[i]))
        {
            std[a[i]] = min(std[a[i]], b[i]);
        }
        else std.insert(pair<int, long long int>(a[i], b[i]));
    }
    
    for(int i = 1; i < n; i++)
    {
        map<int, long long int>::iterator it;
        for(it = std.begin(); it != std.end(); it++)
        {
            int ans = gcd(it->first, a[i]);
            if(std.count(ans))
            {
                std[ans] = min((long long)it->second + b[i], std[ans]);
            }
            else {
                std.insert(pair<int, long long int>(ans, (long long)b[i] + it->second));
            }
        }
    }
    if(std.count(1))
        cout<<std[1]<<endl;
    else
        cout<<-1<<endl;
    return 0;
}