STL priority_queue - 优先队列

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // 默认是最大堆
    priority_queue<int> pq;
    
    // 插入元素
    pq.push(3);
    pq.push(1);
    pq.push(4);
    pq.push(1);
    pq.push(5);
    
    // 访问堆顶（最大元素）
    cout << "堆顶: " << pq.top() << endl;  // 5
    
    // 删除堆顶
    pq.pop();
    cout << "删除后堆顶: " << pq.top() << endl;  // 4
    
    // 遍历（会破坏堆结构）
    while (!pq.empty())
    {
        cout << pq.top() << " ";
        pq.pop();
    }
    // 输出: 4 3 1 1
    
    return 0;
}

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // 最小堆
    priority_queue<int, vector<int>, greater<int>> pq;
    
    // 插入元素
    pq.push(3);
    pq.push(1);
    pq.push(4);
    pq.push(1);
    pq.push(5);
    
    // 访问堆顶（最小元素）
    cout << "堆顶: " << pq.top() << endl;  // 1
    
    // 遍历
    while (!pq.empty())
    {
        cout << pq.top() << " ";
        pq.pop();
    }
    // 输出: 1 1 3 4 5
    
    return 0;
}

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;

struct Node
{
    int val, priority;
    Node(int v, int p) : val(v), priority(p) {}
    
    // 重载 < 运算符，用于最大堆
    bool operator<(const Node& other) const
    {
        return priority < other.priority;  // 大的优先级优先
    }
};

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    priority_queue<Node> pq;
    pq.emplace(1, 10);
    pq.emplace(2, 5);
    pq.emplace(3, 15);
    
    while (!pq.empty())
    {
        Node top = pq.top();
        cout << "val: " << top.val << ", priority: " << top.priority << endl;
        pq.pop();
    }
    // 输出:
    // val: 3, priority: 15
    // val: 1, priority: 10
    // val: 2, priority: 5
    
    return 0;
}

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;

struct Node
{
    int val, cost;
    Node(int v, int c) : val(v), cost(c) {}
};

// 自定义比较器（最小堆，按 cost 排序）
struct Compare
{
    bool operator()(const Node& a, const Node& b)
    {
        return a.cost > b.cost;  // 小的 cost 优先
    }
};

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    priority_queue<Node, vector<Node>, Compare> pq;
    pq.emplace(1, 100);
    pq.emplace(2, 50);
    pq.emplace(3, 150);
    
    while (!pq.empty())
    {
        Node top = pq.top();
        cout << "val: " << top.val << ", cost: " << top.cost << endl;
        pq.pop();
    }
    // 输出:
    // val: 2, cost: 50
    // val: 1, cost: 100
    // val: 3, cost: 150
    
    return 0;
}

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;

using ll = long long;
using pii = pair<ll, int>;  // (距离, 节点)

const ll INF = 1e18;

vector<ll> dijkstra(int start, const vector<vector<pii>>& g)
{
    int n = g.size();
    vector<ll> dist(n, INF);
    dist[start] = 0;
    
    // 最小堆，按距离排序
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    pq.emplace(0, start);
    
    while (!pq.empty())
    {
        pair<ll, int> top = pq.top();
        ll d = top.first;
        int u = top.second;
        pq.pop();
        
        if (d > dist[u])
        {
            continue;  // 旧的路径，跳过
        }
        
        for (const auto& edge : g[u])
        {
            int v = edge.first;
            ll w = edge.second;
            if (dist[v] > dist[u] + w)
            {
                dist[v] = dist[u] + w;
                pq.emplace(dist[v], v);
            }
        }
    }
    
    return dist;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m, start;
    cin >> n >> m >> start;
    
    vector<vector<pii>> g(n);
    for (int i = 0; i < m; i++)
    {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].emplace_back(v, w);
    }
    
    vector<ll> dist = dijkstra(start, g);
    for (int i = 0; i < n; i++)
    {
        if (dist[i] == INF)
        {
            cout << "INF ";
        }
        else
        {
            cout << dist[i] << " ";
        }
    }
    
    return 0;
}

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// 活动选择问题（最大不重叠区间）
struct Interval
{
    int start, end;
    bool operator<(const Interval& other) const
    {
        return end > other.end;  // 按结束时间排序（最小堆）
    }
};

int max_non_overlapping(vector<Interval>& intervals)
{
    sort(intervals.begin(), intervals.end(), [](const Interval& a, const Interval& b)
    {
        return a.start < b.start;
    });
    
    priority_queue<Interval> pq;
    int count = 0;
    
    for (const auto& interval : intervals)
    {
        while (!pq.empty() && pq.top().end <= interval.start)
        {
            pq.pop();
        }
        pq.push(interval);
        count = max(count, (int)pq.size());
    }
    
    return count;
}

// 合并 k 个有序链表
struct ListNode
{
    int val;
    ListNode* next;
    ListNode(int x) : val(x), next(nullptr) {}
};

struct CompareNode
{
    bool operator()(ListNode* a, ListNode* b)
    {
        return a->val > b->val;  // 最小堆
    }
};

ListNode* merge_k_lists(vector<ListNode*>& lists)
{
    priority_queue<ListNode*, vector<ListNode*>, CompareNode> pq;
    
    for (ListNode* node : lists)
    {
        if (node)
        {
            pq.push(node);
        }
    }
    
    ListNode dummy(0);
    ListNode* tail = &dummy;
    
    while (!pq.empty())
    {
        ListNode* node = pq.top();
        pq.pop();
        
        tail->next = node;
        tail = tail->next;
        
        if (node->next)
        {
            pq.push(node->next);
        }
    }
    
    return dummy.next;
}

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vector<int> max_sliding_window(vector<int>& nums, int k)
{
    vector<int> res;
    // 最大堆，存储 (值, 索引)
    priority_queue<pair<int, int>> pq;
    
    for (int i = 0; i < nums.size(); i++)
    {
        pq.emplace(nums[i], i);
        
        // 移除窗口外的元素
        while (pq.top().second <= i - k)
        {
            pq.pop();
        }
        
        if (i >= k - 1)
        {
            res.push_back(pq.top().first);
        }
    }
    
    return res;
}

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    priority_queue<pair<int, string>> pq;
    pq.emplace(10, "apple");
    pq.emplace(5, "banana");
    pq.emplace(15, "orange");
    
    while (!pq.empty())
    {
        pair<int, string> top = pq.top();
        int priority = top.first;
        string name = top.second;
        cout << "priority: " << priority << ", name: " << name << endl;
        pq.pop();
    }
    
    return 0;
}

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;

// 自定义比较器（最小堆）
struct Compare
{
    bool operator()(int a, int b)
    {
        return a > b;  // 小的优先
    }
};

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // C++11: 使用函数对象作为比较器
    priority_queue<int, vector<int>, Compare> pq;
    pq.push(3);
    pq.push(1);
    pq.push(4);
    
    while (!pq.empty())
    {
        cout << pq.top() << " ";
        pq.pop();
    }
    // 输出: 1 3 4
    
    return 0;
}

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// 预分配堆的底层容器空间
priority_queue<int> pq;
// 无法直接 reserve，但可以通过构造函数传入预分配的 vector
vector<int> data;
data.reserve(100000);
priority_queue<int> pq2(data.begin(), data.end());

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// 使用 emplace 避免拷贝
priority_queue<Node> pq;
pq.emplace(1, 10);  // 原地构造，比 push(Node(1, 10)) 更高效

// 使用移动语义
priority_queue<vector<int>> pq;
vector<int> v = {1, 2, 3};
pq.push(move(v));  // 移动而非拷贝

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#include <bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;

using ll = long long;
using pii = pair<ll, int>;

const ll INF = 1e18;

// Dijkstra 算法模板
vector<ll> dijkstra(int start, const vector<vector<pii>>& g)
{
    int n = g.size();
    vector<ll> dist(n, INF);
    dist[start] = 0;
    
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    pq.emplace(0, start);
    
    while (!pq.empty())
    {
        pii top = pq.top();
        ll d = top.first;
        int u = top.second;
        pq.pop();
        
        if (d > dist[u])
        {
            continue;
        }
        
        for (const auto& edge : g[u])
        {
            int v = edge.first;
            ll w = edge.second;
            if (dist[v] > dist[u] + w)
            {
                dist[v] = dist[u] + w;
                pq.emplace(dist[v], v);
            }
        }
    }
    
    return dist;
}

// 贪心算法：最大不重叠区间
struct Interval
{
    int start, end;
};

int max_non_overlapping(vector<Interval>& intervals)
{
    sort(intervals.begin(), intervals.end(), [](const Interval& a, const Interval& b)
    {
        return a.start < b.start;
    });
    
    priority_queue<int, vector<int>, greater<int>> pq;  // 存储结束时间
    int count = 0;
    
    for (const auto& interval : intervals)
    {
        while (!pq.empty() && pq.top() <= interval.start)
        {
            pq.pop();
        }
        pq.push(interval.end);
        count = max(count, (int)pq.size());
    }
    
    return count;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    // 测试 Dijkstra
    int n, m, start;
    cin >> n >> m >> start;
    
    vector<vector<pii>> g(n);
    for (int i = 0; i < m; i++)
    {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].emplace_back(v, w);
    }
    
    vector<ll> dist = dijkstra(start, g);
    for (ll d : dist)
    {
        cout << (d == INF ? "INF" : to_string(d)) << " ";
    }
    cout << endl;
    
    return 0;
}