一、1.排序 - 蓝桥云课

（快速排序）算法代码：

#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 10;
int a[N];

int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    
    sort(a, a + n);
    
    for (int i = 0; i < n; i++) {
        cout << a[i] << " ";
    }
    cout << endl;
    
    for (int i = n - 1; i >= 0; i--) {
        cout << a[i] << " ";
    }
    cout << endl;
    /*reverse(a,a+n);
    for (int i = 0; i < n; i++) {
        cout << a[i] << " ";
    }*/
    
    return 0;
}

---

二、2.走迷宫 - 蓝桥云课

（BFS）算法代码：

#include <bits/stdc++.h>
using namespace std;

int n, m; // 地图大小
int start_x, start_y, end_x, end_y; // 起始点和终点（1-based）
vector<vector<int>> mp; // 地图（0-based）
vector<vector<int>> path_len; // 记录路径长度
typedef pair<int, int> PII;

// 四个方向偏移量
const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, 1, -1};

int main() {
    cin >> n >> m;
    mp.resize(n, vector<int>(m));
    path_len.resize(n, vector<int>(m, -1)); // 初始化为-1

    // 输入地图（按行优先顺序，1-based转换为0-based）
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> mp[i][j];
        }
    }

    // 输入起始点和目标点坐标（1-based）
    cin >> start_x >> start_y >> end_x >> end_y;
    // 转换为0-based
    start_x--; start_y--; end_x--; end_y--;

    queue<PII> q;
    q.push({start_x, start_y});
    path_len[start_x][start_y] = 0; // 起点算作1个格子

    while (!q.empty()) {
        PII tmp = q.front();
        q.pop();

        // 遍历四个方向
        for (int i = 0; i < 4; i++) {
            int nx = tmp.first + dx[i];
            int ny = tmp.second + dy[i];

            // 检查边界
            if (nx < 0 || ny < 0 || nx >= n || ny >= m) {
                continue;
            }

            // 检查障碍物和是否已访问
            if (mp[nx][ny] == 0 || path_len[nx][ny] != -1) {
                continue;
            }

            path_len[nx][ny] = path_len[tmp.first][tmp.second] + 1;
            q.push({nx, ny});
        }
    }

    // 输出结果（若无法到达则输出-1）
    cout << path_len[end_x][end_y] << endl;

    return 0;
}

---

三、3.小明的背包1 - 蓝桥云课

算法代码：

贪心、但只能通过18.2%：

#include <iostream>
#include <algorithm>
using namespace std;

struct Item {
    int w, v;
};

// 定义结构体的比较规则
bool cmp(const Item& a, const Item& b) {
    if (a.v == b.v) {
        return a.w < b.w;
    }
    return a.v > b.v;
}

int main() {
    int n, V;  // 注意这里改为大写的V表示背包容量
    cin >> n >> V;  // 必须先读取n和V的值
    
    Item items[105];
    for (int i = 0; i < n; i++) {
        cin >> items[i].w >> items[i].v;
    }

    // 按价值从大到小来排列
    sort(items, items + n, cmp);
    
    // 从价值最大的物品放入
    int sum = 0;
    int remaining = V;  // 剩余容量
    for (int i = 0; i < n; i++) {
        if (remaining >= items[i].w) {
            sum += items[i].v;
            remaining -= items[i].w;
        }
    }
    cout << sum << endl;
    return 0;
}

 动态规划：

#include<bits/stdc++.h>
using namespace std;

const int MAXN = 110;
const int MAXV = 1010;

int N, V;
int w[MAXN], v[MAXN];
int f[MAXN][MAXV];

int main() {
    cin >> N >> V;
    for (int i = 1; i <= N; i++) {
        cin >> w[i] >> v[i];
    }

    memset(f, 0, sizeof(f));
    for (int i = 1; i <= N; i++) {
        for (int j = 0; j <= V; j++) {
            f[i][j] = f[i - 1][j];//不放
            if (j >= w[i])// 背包还有空间
            {
                f[i][j] = max(f[i][j], f[i - 1][j - w[i]] + v[i]);
            }
        }
    }

    cout << f[N][V] << endl;
    return 0;
}

---

四、4.蓝桥公园 - 蓝桥云课

（Floyd）算法代码： 

#include<bits/stdc++.h>
using namespace std;
using ll =long long;
const int N=500;
ll inf=1e18;
ll n,m,q;
ll d[N][N];
int main()
{
    cin>>n>>m>>q;
  for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
        {
            d[i][j]=inf;
        }
    }
    for(int i=1;i<=n;i++)d[i][i]=0;
    while(m--)
    {
        ll u,v,w;cin>>u>>v>>w;
        d[u][v]=min(d[u][v],w);
        d[v][u]=min(d[v][u],w); 
    }
    for(int k=1;k<=n;k++)
    {
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=n;j++)
            {
                d[i][j]=min(d[i][j],d[i][k]+d[k][j]);
            }
        }
    }
    while(q--)
    {
        int st,ed;cin>>st>>ed;
        cout<<(d[st][ed]>=inf ? -1 : d[st][ed])<<endl;
    }
    return 0;
}

---

五、5.回文判定 - 蓝桥云课

（字符串、模拟、双指针）算法代码： 

#include <bits/stdc++.h>
using namespace std;
int main()
{
    string s;
    cin>>s;
    int left=0;
    int right=s.size()-1;
    while(left<right)
    {
        if(s[left]!=s[right])
        {
            cout<<"N"<<endl;
            return 0;
        }
        left++;
        right--;
    }
    cout<<"Y"<<endl;
    return 0;
}

---

六、6.小明的彩灯 - 蓝桥云课

（差分）算法代码： 

#include <iostream>
#include <vector>
#define int long long 
using namespace std;

signed main() {
    int n, q;
    cin >> n >> q;

    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    vector<int> d(n + 1, 0);  // 差分数组，长度为 n+1
    for (int i = 0; i < q; i++) {
        int l, r, x;
        cin >> l >> r >> x;
        d[l] += x;
        if (r < n) {
            d[r + 1] -= x;
        }
    }

    // 对差分数组进行前缀和操作，即可得到每个彩灯的最终亮度
    for (int i = 1; i <= n; i++) {
        d[i] += d[i - 1];
        a[i - 1] += d[i];
        if (a[i - 1] < 0) {
            a[i - 1] = 0;
        }
    }

    for (int i = 0; i < n; i++) {
        cout << a[i] << " ";
    }
    cout << endl;

    return 0;
}

---

七、7.解立方根 - 蓝桥云课

（二分）算法代码：（只能25%，这个题有问题） 

#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

const double eps = 1e-8;

double cube_root(double x) {
    double l = 0, r = x;
    while (r - l > eps) {
        double mid = (l + r) / 2;
        if (mid * mid * mid < x) {
            l = mid;
        } else {
            r = mid;
        }
    }
    return l;
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        int x;
        cin >> x;
        double ans = cube_root(x);
        printf("%.3f\n", ans);
    }
    return 0;
}

---

八、10.蓝桥骑士 - 蓝桥云课

（LIS）算法代码： 

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    int n;
    cin >> n;

    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    vector<int> S;
    for (int i = 0; i < n; i++) {
        if (S.empty() || a[i] > S.back()) {
            S.push_back(a[i]);
        } else {
            auto it = lower_bound(S.begin(), S.end(), a[i]);
            *it = a[i];
        }
    }

    cout << S.size() << endl;

    return 0;
}

---

九、8.蓝桥幼儿园 - 蓝桥云课

（并查集）算法代码：

#include <iostream>
#include <vector>

using namespace std;

const int MAXN = 2e5 + 5;

int fa[MAXN];

// 并查集的查找操作
int find(int x) {
    if (fa[x] != x) {
        fa[x] = find(fa[x]);
    }
    return fa[x];
}

int main() {
    int n, m;
    cin >> n >> m;

    // 初始化每个人的父亲为自己
    for (int i = 1; i <= n; ++i) {
        fa[i] = i;
    }

    // 处理操作
    while (m--) {
        int op, x, y;
        cin >> op >> x >> y;
        if (op == 1) {
            int fx = find(x), fy = find(y);
            // 将两个人所在的连通分量合并
            if (fx != fy) {
                fa[fx] = fy;
            }
        } else {
            int fx = find(x), fy = find(y);
            // 判断两个人是否在同一个连通分量中
            if (fx == fy) {
                cout << "YES" << endl;
            } else {
                cout << "NO" << endl;
            }
        }
    }

    return 0;
}

---

十、9.蓝桥王国 - 蓝桥云课

（Dijkstra）算法代码： 

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const long long INF = 0x3f3f3f3f3f3f3f3fLL;
const int MAXN = 3e5 + 2;

struct Edge {
    int from, to;
    long long weight;
    Edge(int u, int v, long long w) : from(u), to(v), weight(w) {}
};

vector<Edge> edges[MAXN];

struct Node {
    int id;
    long long dis;
    Node(int i, long long d) : id(i), dis(d) {}
    bool operator<(const Node& other) const {
        return dis > other.dis;
    }
};

int n, m;
long long dist[MAXN];

void dijkstra() {
    int start = 1;
    bool visited[MAXN] = {false};
    for (int i = 1; i <= n; i++) {
        dist[i] = INF;
        visited[i] = false;
    }
    dist[start] = 0;
    priority_queue<Node> pq;
    pq.push(Node(start, dist[start]));
    while (!pq.empty()) {
        Node u = pq.top();
        pq.pop();
        if (visited[u.id])
            continue;
        visited[u.id] = true;
        for (int i = 0; i < edges[u.id].size(); i++) {
            Edge e = edges[u.id][i];
            if (visited[e.to])
                continue;
            if (dist[e.to] > e.weight + u.dis) {
                dist[e.to] = e.weight + u.dis;
                pq.push(Node(e.to, dist[e.to]));
            }
        }
    }
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        edges[i].clear();
    }
    while (m--) {
        int u, v, w;
        cin >> u >> v >> w;
        edges[u].push_back(Edge(u, v, w));
    }
    dijkstra();
    for (int i = 1; i <= n; i++) {
        if (dist[i] >= INF) {
            cout << "-1" << " ";
        } else {
            cout << dist[i] << " ";
        }
    }
    return 0;
}