非变异算法

#include <algorithm>
#include <numeric>

std::vector<int> v{1, 3, 5, 7, 9};
auto it = std::find(v.begin(), v.end(), 5);     // 查找
auto n  = std::count(v.begin(), v.end(), 3);    // 计数

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

struct Candidate {
    std::string name;
    int score;
    int experience;  // 经验年限
    std::string skill;
};

void printCandidates(const std::string& title,
                     const std::vector<Candidate>& candidates) {
    std::cout << title << ":\n";
    for (const auto& c : candidates)
        std::cout << "  " << c.name << " | 分数:" << c.score
                  << " | 经验:" << c.experience << "年"
                  << " | 技能:" << c.skill << "\n";
}

int main() {
    std::vector<Candidate> pool = {
        {"大翔", 98, 8, "C++"},
        {"白歌", 95, 10, "架构设计"},
        {"小崔", 92, 5, "后端开发"},
        {"黄俪", 90, 4, "前端开发"},
        {"李眉", 88, 7, "运维"},
        {"孔蓝", 87, 5, "产品"},
        {"赵鸣", 85, 3, "运营"},
        {"孙鹤", 82, 1, "产品助理"},
    };

    // 1. find：精确查找
    auto it = std::find_if(pool.begin(), pool.end(),
        [](const Candidate& c) { return c.name == "白歌"; });
    if (it != pool.end())
        std::cout << "[find] 找到: " << it->name << ", 分数: " << it->score << "\n";

    // 2. count：统计
    int senior = std::count_if(pool.begin(), pool.end(),
        [](const Candidate& c) { return c.experience >= 5; });
    std::cout << "[count] 高级人才(>=5年): " << senior << " 人\n";

    // 3. search：子序列匹配
    std::vector<std::string> targetSkills{"C++", "架构设计"};
    // 查找连续两个候选人技能匹配 targetSkills
    auto searchIt = std::search(pool.begin(), pool.end(),
        targetSkills.begin(), targetSkills.end(),
        [](const Candidate& c, const std::string& skill) {
            return c.skill == skill;
        });
    if (searchIt != pool.end())
        std::cout << "[search] 技能序列匹配起点: " << searchIt->name << "\n";

    // 4. equal：比较两组数据
    std::vector<int> expectedScores{98, 95, 92, 90};
    std::vector<int> actualScores;
    for (const auto& c : pool) actualScores.push_back(c.score);

    bool scoresMatch = std::equal(expectedScores.begin(),
        expectedScores.end(), actualScores.begin());
    std::cout << "[equal] 分数匹配预期: " << std::boolalpha << scoresMatch << "\n";

    // 5. all_of / any_of / none_of
    bool allQualified = std::all_of(pool.begin(), pool.end(),
        [](const Candidate& c) { return c.score >= 80; });
    bool hasSenior = std::any_of(pool.begin(), pool.end(),
        [](const Candidate& c) { return c.experience >= 10; });

    std::cout << "[all_of] 全部 >= 80 分: " << allQualified << "\n";
    std::cout << "[any_of] 有经验 >= 10 年: " << hasSenior << "\n";

    // 6. minmax_element
    auto [minIt, maxIt] = std::minmax_element(pool.begin(), pool.end(),
        [](const Candidate& a, const Candidate& b) {
            return a.score < b.score;
        });
    std::cout << "[minmax] 最低: " << minIt->name << "(" << minIt->score
              << "), 最高: " << maxIt->name << "(" << maxIt->score << ")\n";
}

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <iomanip>

struct LogEntry {
    std::string timestamp;
    std::string level;
    std::string message;
    bool audited = false;
};

int main() {
    std::vector<LogEntry> logs = {
        {"2026-06-14 09:00", "INFO",  "飞翔科技-服务启动"},
        {"2026-06-14 09:05", "WARN",  "飞翔科技-内存使用 85%"},
        {"2026-06-14 09:10", "ERROR", "飞翔科技-数据库连接超时"},
        {"2026-06-14 09:15", "INFO",  "飞翔科技-用户登录: 孔蓝"},
        {"2026-06-14 09:20", "ERROR", "飞翔科技-支付回调失败"},
    };

    int errorCount = 0;

    // for_each：遍历并执行操作（不修改容器，但可修改元素属性）
    std::for_each(logs.begin(), logs.end(),
        [&errorCount](LogEntry& entry) {
            entry.audited = true;

            if (entry.level == "ERROR") {
                ++errorCount;
                entry.message += " [需紧急处理]";
            } else if (entry.level == "WARN") {
                entry.message += " [关注]";
            }
        });

    std::cout << "=== 飞翔科技日志审计 ===\n";
    std::cout << "总共 " << logs.size() << " 条，ERROR " << errorCount << " 条\n\n";

    for (const auto& log : logs) {
        std::cout << log.timestamp << " [" << log.level << "] "
                  << log.message;
        std::cout << " (audited: " << log.audited << ")\n";
    }
}

auto it = std::find(v.begin(), v.end(), 999);
// std::cout << *it;  // ❌ 如果 it == end()，解引用是未定义行为
if (it != v.end()) std::cout << *it;  // ✅

std::vector<int> a{1, 2, 3, 4};
std::vector<int> b{1, 2};
// std::equal(a.begin(), a.end(), b.begin());  // ❌ b 不够长

auto result = std::min(5, 3.14);  // ❌ 编译错误！int vs double
auto result2 = std::min<double>(5, 3.14);  // ✅ 显式指定类型