C++ STL容器操作：6种常用场景算法

引言

在日常软件开发工作中，容器操作如查找、排序、和元素替换等任务极为常见。幸运的是，C++的标准化利器——STL（Standard Template Library，标准模板库）为我们封装了一系列高效且灵活的算法，极大简化了这些操作。特别是自C++11版本以来，STL引入了一批新晋的通用算法，它们不仅功能强大，而且设计得更加人性化，旨在进一步提升我们的编码效率与程序性能。本文列举一些常用到的方法，便于日后回顾和查阅。

概述

日常开发中的容器操作，如查找、删除、排序、分割、拷贝和合并，均可借助STL中的精选算法高效完成。本文将概览这些核心STL算法，助力开发流程优化。

查找与计数

std::find

作用：找容器中第一个匹配给定值的元素

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};
  DumpVector("testArrgs", testArrgs);

  auto find = std::find(testArrgs.begin(), testArrgs.end(), "XiaoMing");
  if (find != testArrgs.end()) {
      SPR_LOGD("find: dest = \"XiaoMing\", result = %s, index = %ld\n", find->c_str(), find - testArrgs.begin());
  }

结果

D: find: dest = "XiaoMing", result = XiaoMing, index = 2

std::find_if

作用：查找容器中第一个满足谓词条件的元素

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  auto findIf = std::find_if(testArrgs.begin(), testArrgs.end(),  [](const std::string &str) { return str.find("Ming") != std::string::npos; });
  if (findIf != testArrgs.end()) {
      SPR_LOGD("find_if: dest = \"Ming\", result = %s, index = %ld\n", findIf->c_str(), findIf - testArrgs.begin());
  }

③ 结果

D: find_if: dest = "Ming", result = XiaoMing, index = 2

std::find_if_not

作用：寻找第一个不符合指定条件的元素

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  auto findIfNot = std::find_if_not(testArrgs.begin(), testArrgs.end(),  [](const std::string &str) { return str.find("Xiao") != std::string::npos; });
  if (findIfNot != testArrgs.end()) {
      SPR_LOGD("find_if_not: dest = \"Xiao\", result = %s, index = %ld\n", findIfNot->c_str(), findIfNot - testArrgs.begin());
  }

结果

D: find_if_not: dest = "Xiao", result = LiHua, index = 1

std::find_end

作用：查找一个子序列最后一次出现的位置

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> subArrgs1 = {"XiaoMing", "XiaoHong"};
  auto findEnd = std::find_end(testArrgs.begin(), testArrgs.end(), subArrgs1.begin(), subArrgs1.end());
  if (findEnd != testArrgs.end()) {
      SPR_LOGD("find_end: dest = {\"XiaoMing\", \"XiaoHong\"}, result = %s, index = %ld\n", findEnd->c_str(), findEnd - testArrgs.begin());
  }

结果

D: find_end: dest = {"XiaoMing", "XiaoHong"}, result = XiaoMing, index = 3

std::find_first_of

作用：查找序列中任何一个元素首次出现的位置

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> subArrgs2 = {"JianGuo"};
  auto findFirstOf = std::find_first_of(testArrgs.begin(), testArrgs.end(), subArrgs2.begin(), subArrgs2.end());
  if (findFirstOf != testArrgs.end()) {
      SPR_LOGD("find_first_of: dest = {\"JianGuo\"}, result = %s, index = %ld\n", findFirstOf->c_str(), findFirstOf - testArrgs.begin());
  }

结果

D: find_first_of: dest = {"JianGuo"}, result = JianGuo, index = 5

std::adjacent_find

作用：查找相邻重复的元素

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  auto adjacentFind = std::adjacent_find(testArrgs.begin(), testArrgs.end(), [](const std::string &str1, const std::string &str2) { return str1 == str2; });
  if (adjacentFind != testArrgs.end()) {
      SPR_LOGD("adjacent_find: result = %s, index = %ld\n", adjacentFind->c_str(), adjacentFind - testArrgs.begin());
  }

结果

D: adjacent_find: result = XiaoMing, index = 2

std::count

作用：计算容器中指定值出现的次数

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  auto cnt = std::count(testArrgs.begin(), testArrgs.end(), "XiaoFang");
  if (cnt > 0) {
      SPR_LOGD("count: dest = \"XiaoFang\", result = %ld\n", cnt);
  }

结果

D: count: dest = "XiaoFang", result = 1

std::count_if

作用：计算满足谓词条件的元素数量

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  auto cntIf = std::count_if(testArrgs.begin(), testArrgs.end(), [](const std::string &str) { return str.find("Xiao") != std::string::npos; });
  if (cntIf > 0) {
      SPR_LOGD("count_if: dest = \"Xiao\", result = %ld\n", cntIf);
  }

结果
```
D: count_if: dest = "Xiao", result = 6
```

移除与替换

std::remove

作用：重新排列容器元素，使得所有不匹配特定值的元素被放置在容器的前端。配合earse实现移除不匹配元素。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> rmArrgs(testArrgs);
  auto remove = std::remove(rmArrgs.begin(), rmArrgs.end(), "XiaoMing");
  if (remove != rmArrgs.end()) {
      rmArrgs.erase(remove, rmArrgs.end());
      DumpVector("rmArrgs", rmArrgs);
  }

结果

D: rmArrgs: "XiaoFang", "LiHua", "XiaoHong", "JianGuo", "XiaoFangFang",

std::remove_if

作用：重新排列容器元素，使得所有不满足谓词条件的元素被放置在容器的前端。配合earse实现移除不匹配元素。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> rmIfArrgs(testArrgs);
  auto removeIf = std::remove_if(rmIfArrgs.begin(), rmIfArrgs.end(), [](const std::string &str) { return str.find("Xiao") != std::string::npos; });
  if (removeIf != rmIfArrgs.end()) {
      rmIfArrgs.erase(removeIf, rmIfArrgs.end());
      DumpVector("rmArrgs", rmArrgs);
  }

结果

D: rmIfArrgs: "XiaoFang", "LiHua", "XiaoHong", "JianGuo", "XiaoFangFang"

std::remove_copy

作用：从源序列拷贝元素到目标序列，排除满足条件的元素。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> dstArrgs;
  vector<std::string> rcArrgs(testArrgs);
  std::remove_copy(rcArrgs.begin(), rcArrgs.end(), std::back_inserter(dstArrgs), "XiaoMing");
  DumpVector("dstArrgs", dstArrgs);

结果

D: dstArrgs: "XiaoFang", "LiHua", "XiaoHong", "JianGuo", "XiaoFangFang"

std::replace

作用：将所有出现的指定元素替换为新值。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> rpArrgs(testArrgs);
  std::replace(rpArrgs.begin(), rpArrgs.end(), "XiaoMing", "MingMing");
  DumpVector("rpArrgs", rpArrgs);

结果

D: rpArrgs: "XiaoFang", "LiHua", "MingMing", "MingMing", "XiaoHong", "JianGuo", "XiaoFangFang", "MingMing",

std::replace_if

作用：满足谓词条件的元素，替换为指定的替换值。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> rpIfArrgs(testArrgs);
  std::replace_if(rpIfArrgs.begin(), rpIfArrgs.end(), [](const std::string &str) { return (str == "XiaoFang"); }, "FangFang");
  DumpVector("rpIfArrgs", rpIfArrgs);

结果

D: rpIfArrgs: "FangFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing",

std::replace_copy

作用：用于在指定范围内将所有匹配某个值的元素替换为另一个值，拷贝到另一个的容器中。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> rpCpDstArrgs;
  vector<std::string> rpCopyArrgs(testArrgs);
  std::replace_copy(rpCopyArrgs.begin(), rpCopyArrgs.end(), std::back_inserter(rpCpDstArrgs), "XiaoMing", "MingMing");
  DumpVector("rpCpDstArrgs", rpCpDstArrgs);

结果

D: rpCpDstArrgs: "XiaoFang", "LiHua", "MingMing", "MingMing", "XiaoHong", "JianGuo", "XiaoFangFang", "MingMing"

std::swap

作用：交换两个变量的值。

示例

  vector<std::string> testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

  vector<std::string> swapSrcArrgs(testArrgs);
  vector<std::string> swapDstArrgs = {"Vince Carter", "Rose", "James"};
  std::swap(swapSrcArrgs, swapDstArrgs);
  DumpVector("swapSrcArrgs", swapSrcArrgs);
  DumpVector("swapDstArrgs", swapDstArrgs);

结果

D: swapSrcArrgs: "Vince Carter", "Rose", "James", 
D: swapDstArrgs: "XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing",

排序与组织

std::sort

作用：对容器元素进行排序。
示例
```c++
vector testArrgs = {"XiaoFang", "LiHua", "XiaoMing", "XiaoMing", "XiaoHong", "JianGuo", "XiaoFangFang", "XiaoMing"};

// sort
vector sortArrgs(testArrgs);
std::sort(sortArrgs.begin(), sortArrgs.end());
DumpVector("sortArrgs", sortArrgs);
std::sort(sortArrgs.begin(), sortArrgs.end(), { return str1.size() > str2.size(); });
DumpVector("sortArrgs", sortArrgs);

* 结果
```c++
  D: sortArrgs: "JianGuo", "LiHua", "XiaoFang", "XiaoFangFang", "XiaoHong", "XiaoMing", "XiaoMing", "XiaoMing", 
  D: sortArrgs: "XiaoFangFang", "XiaoFang", "XiaoHong", "XiaoMing", "XiaoMing", "XiaoMing", "JianGuo", "LiHua",

std::stable_sort

作用：稳定排序，保持相等元素的原有顺序。

示例

  // stable_sort
  vector<Persion> srcPersions = {
    {"LiWei", 18}, {"LiHua", 20}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"ZhenHua", 20}, {"JianGuo", 18}, {"ZhiGuo", 19}, {"JianHua", 19}};
  vector<Persion> sPersions(srcPersions);
  std::stable_sort(sPersions.begin(), sPersions.end(), [](const Persion &p1, const Persion &p2) { return p1.age > p2.age; });
  DumpVector("sPersions", sPersions);
  std::stable_sort(sPersions.begin(), sPersions.end(), [](const Persion &p1, const Persion &p2) { return p1.age < p2.age; });
  DumpVector("sPersions", sPersions);

结果

D: sPersions = { {"LiHua", 20}, {"ZhenHua", 20}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"ZhiGuo", 19}, {"JianHua", 19}, {"LiWei", 18}, {"JianGuo", 18}, }
D: sPersions = { {"LiWei", 18}, {"JianGuo", 18}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"ZhiGuo", 19}, {"JianHua", 19}, {"LiHua", 20}, {"ZhenHua", 20}, }

std::partial_sort

作用：对部分区间排序。

示例

  vector<Persion> srcPersions = {
    {"LiWei", 18}, {"LiHua", 20}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"ZhenHua", 20}, {"JianGuo", 18}, {"ZhiGuo", 19}, {"JianHua", 19}};

  // partial_sort
  vector<Persion> prtPersions(srcPersions);
  vector<Persion> sortPersions(srcPersions);
  std::partial_sort(prtPersions.begin(), prtPersions.begin() + 5, prtPersions.end(), [](const Persion &p1, const Persion &p2) { return p1.age > p2.age; });
  std::sort(sortPersions.begin(), sortPersions.begin() + 5, [](const Persion &p1, const Persion &p2) { return p1.age > p2.age; });
  DumpVector("prtPersions", prtPersions);
  DumpVector("sortPersions", sortPersions);

结果

D: prtPersions = { {"ZhenHua", 20}, {"LiHua", 20}, {"WeiGuo", 19}, {"ZhiGuo", 19}, {"ZhangLei", 19}, {"JianGuo", 18}, {"LiWei", 18}, {"JianHua", 19}, }
D: sortPersions = { {"LiHua", 20}, {"ZhenHua", 20}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"LiWei", 18}, {"JianGuo", 18}, {"ZhiGuo", 19}, {"JianHua", 19}, }

std::reverse

作用：对部分区间排序。

示例

  vector<Persion> srcPersions = {
    {"LiWei", 18}, {"LiHua", 20}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"ZhenHua", 20}, {"JianGuo", 18}, {"ZhiGuo", 19}, {"JianHua", 19}};

  // reverse
  vector<Persion> rPersions(srcPersions);
  std::reverse(rPersions.begin(), rPersions.end());
  DumpVector("rPersions", rPersions);

结果

D: rPersions = { {"JianHua", 19}, {"ZhiGuo", 19}, {"JianGuo", 18}, {"ZhenHua", 20}, {"WeiGuo", 19}, {"ZhangLei", 19}, {"LiHua", 20}, {"LiWei", 18}, }

std::rotate

作用：对部分区间排序。

示例

  vector<Persion> srcPersions = {
    {"LiWei", 18}, {"LiHua", 20}, {"ZhangLei", 19}, {"WeiGuo", 19}, {"ZhenHua", 20}, {"JianGuo", 18}, {"ZhiGuo", 19}, {"JianHua", 19}};

  // rotate
  vector<Persion> rtPersions(srcPersions);
  std::rotate(rtPersions.begin(), rtPersions.begin() + 3, rtPersions.end());
  DumpVector("rtPersions", rtPersions);

结果

D: rPersions = { {"JianHua", 19}, {"ZhiGuo", 19}, {"JianGuo", 18}, {"ZhenHua", 20}, {"WeiGuo", 19}, {"ZhangLei", 19}, {"LiHua", 20}, {"LiWei", 18}, }

分割

std::partition

作用：分割容器，使满足谓词的元素在前，不满足的在后。

示例

  vector<std::string> testArrgs = {"LiHua", "ZhangHong", "HeDa", "LiWei", "ZhangLei", "WeiGuo", "ZhenHua"};

  // partition
  vector<std::string> partArrgs(testArrgs);
  std::partition(partArrgs.begin(), partArrgs.end(), [](const std::string& str) { return (str.compare(0, 5, "Zhang") == 0); });
  DumpVector("partArrgs", partArrgs);

结果

D: partArrgs: "ZhangLei", "ZhangHong", "HeDa", "LiWei", "LiHua", "WeiGuo", "ZhenHua",

std::stable_partition

作用：类似partition，但保持相同元素的相对顺序不变。

示例

  vector<std::string> testArrgs = {"LiHua", "ZhangHong", "HeDa", "LiWei", "ZhangLei", "WeiGuo", "ZhenHua"};

  // stable_partition
  vector<std::string> stPartArrgs(testArrgs);
  std::stable_partition(stPartArrgs.begin(), stPartArrgs.end(), [](const std::string& str) { return (str.compare(0, 5, "Zhang") == 0); });
  DumpVector("stPartArrgs", stPartArrgs);

结果

D: stPartArrgs: "ZhangHong", "ZhangLei", "LiHua", "HeDa", "LiWei", "WeiGuo", "ZhenHua",

拷贝与生成

std::copy

作用：拷贝容器或范围内的元素到另一位置。

示例

  vector<std::string> srcArrgs = {"LiHua", "ZhangHong", "HeDa", "LiWei", "ZhangLei", "WeiGuo", "ZhenHua"};

  // copy
  vector<std::string> dstCopyArrgs;
  std::copy(srcArrgs.begin(), srcArrgs.end(), std::back_inserter(dstCopyArrgs));
  DumpVector("dstCopyArrgs", dstCopyArrgs);

结果

D: dstCopyArrgs: "LiHua", "ZhangHong", "HeDa", "LiWei", "ZhangLei", "WeiGuo", "ZhenHua",

std::copy_if

作用：根据谓词条件拷贝元素。

示例

  vector<std::string> srcArrgs = {"LiHua", "ZhangHong", "HeDa", "LiWei", "ZhangLei", "WeiGuo", "ZhenHua"};

  // copy_if
  vector<std::string> dstCopyIfArrgs;
  std::copy_if(srcArrgs.begin(), srcArrgs.end(), std::back_inserter(dstCopyIfArrgs), [](const std::string& str) { return (str.compare(0, 5, "Zhang") == 0); });
  DumpVector("dstCopyIfArrgs", dstCopyIfArrgs);

结果

D: dstCopyIfArrgs: "ZhangHong", "ZhangLei",

std::copy_n

作用：拷贝指定数量的元素。

示例

  vector<std::string> srcArrgs = {"LiHua", "ZhangHong", "HeDa", "LiWei", "ZhangLei", "WeiGuo", "ZhenHua"};

  // copy_n
  vector<std::string> dstCopyNArrgs;
  std::copy_n(srcArrgs.begin(), 3, std::back_inserter(dstCopyNArrgs));
  DumpVector("dstCopyNArrgs", dstCopyNArrgs);

结果

D: dstCopyNArrgs: "LiHua", "ZhangHong", "HeDa",

std::generate

作用：使用生成器函数填充容器。

示例

  // generate
  vector<std::string> genArrgs(5);
  std::generate(genArrgs.begin(), genArrgs.end(), [](){ return "Hello"; });
  DumpVector("genArrgs", genArrgs);

结果

D: genArrgs: "Hello", "Hello", "Hello", "Hello", "Hello",

std::generate_n

作用：生成指定数量的元素填充容器。

示例

  // generate_n
  vector<std::string> genNArrgs;
  std::generate_n(std::back_inserter(genNArrgs), 3, [](){ return "Hello"; });
  DumpVector("genNArrgs", genNArrgs);

结果

D: genNArrgs: "Hello", "Hello", "Hello",

集合操作

std::merge

作用：生成指定数量的元素填充容器。

示例

  vector<std::string> srcArrgs = {"Vince Carter", "Rose", "James"};

  // merge
  vector<std::string> mergeArrgs;
  vector<std::string> tmpArrgs = {"Irving"};
  std::merge(srcArrgs.begin(), srcArrgs.end(), tmpArrgs.begin(), tmpArrgs.end(), std::back_inserter(mergeArrgs));
  DumpVector("mergeArrgs", mergeArrgs);

结果

D: mergeArrgs: "Irving", "Vince Carter", "Rose", "James",

std::inplace_merge

作用：就地归并两个有序范围。

示例

  vector<std::string> srcArrgs = {"Vince Carter", "Rose", "James"};

  // inplace_merge
  vector<std::string> inplaceMergeArrgs(srcArrgs);
  std::inplace_merge(inplaceMergeArrgs.begin(), inplaceMergeArrgs.begin() + 2, inplaceMergeArrgs.end());
  DumpVector("inplaceMergeArrgs", inplaceMergeArrgs);

结果

D: inplaceMergeArrgs: "James", "Vince Carter", "Rose",

【常用技巧】C++ STL容器操作：6种常用场景算法