文章目录

• • 一、前言
  • 二、构造函数
  • 三、遍历
  • 四、增删查改
  • • • 1.常用接口
      • 2.增删查改
  • 五、经典题目

一、前言

学习完string类之后，我们在来学习vector难度并没有之前那么高，更加容易理解一些接口

vector是表示可变大小数组的序列容器 ，本质讲，vector使用动态分配数组来存储它的元素。

同理，对于vector的使用，我们也要学会去看文档：vector官方文档

本文重点只介绍一些常用的接口

二、构造函数

构造函数的具体介绍直接前往官网查看文档即可，这里只做简单介绍：

对于构造函数，这些与string类似，我们就不在多说，直接上手代码：

void Test()
{vector v;//无参构造vector v1(5, 1);//构造并初始5个1vector v2(v1);//拷贝构造vector v3(++v1.begin(), --v1.end());//迭代器初始化构造
}

此外，对于vector和string的关系是无法替代的，string类中有一个接口c_str()，转化成C语言的字符串要以\0结尾，所以string类最后会有一个\0,在操作上+=,<<,>>等。而vector是保存字符的动态数组，不会以\0结尾，不保存\0，且vector是T泛型，所以并不存在谁替代谁。

三、遍历

1.[]

void Test1()
{vector v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);for (size_t i = 0; i < v.size(); i++){//可读可写v[i]++;cout << v[i] << endl;}
}

2.迭代器、范围for()

正向迭代器和反向迭代器

void Test2()
{vector v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);vector::iterator it = v.begin();while (it != v.end()){(*it)++;cout << *it << " ";it++;}cout << endl;vector::reverse_iterator rit = v.rbegin();while (rit != v.rend()){(*rit)--;cout << *rit << " ";rit++;}cout << endl;}

迭代器很自然和范围for联系起来：

for (auto e : v)
{cout << e << " ";
}
cout << endl;

四、增删查改

1.常用接口

resize&&reserve&&扩容问题

前三个比较容易理解，我们就不说了，我们直接来看resize

void Test3()
{vector v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);cout << v.size() << endl;cout << v.capacity() << endl;v.resize(4);cout << v.size() << endl;cout << v.capacity() << endl;
}

对于reserve:

void Test4()
{vector v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);cout << v.size() << endl;cout << v.capacity() << endl;v.reserve(100);cout << v.size() << endl;cout << v.capacity() << endl;v.reserve(50);cout << v.size() << endl;cout << v.capacity() << endl;
}

capacity扩容问题：

capacity的代码在vs和g++下分别运行会发现，vs下capacity是按1.5倍增长的，g++是按2倍增长的

void Test5()
{size_t sz;std::vector foo;sz = foo.capacity();std::cout << "making foo grow:\n";for (int i = 0; i < 100; ++i) {foo.push_back(i);if (sz != foo.capacity()) {sz = foo.capacity();std::cout << "capacity changed: " << sz << '\n';}}
}

VS下：

Linux的g++下：

2.增删查改

1.push_back和pop_back的用法比较简单：

void Test6()
{vector v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);for (auto e:v){cout << e << " ";}cout << endl;v.pop_back();v.pop_back();for (auto e : v){cout << e << " ";}
}

2.find

注意：算法库中给我们提供一个模板，vector本身并没有find接口，下面我们来看一看：

void Test7()
{vector v;v.push_back(10);v.push_back(20);v.push_back(30);v.push_back(40);v.push_back(50);vector::iterator pos = find(v.begin(), v.end(), 30);//auto pos = find(v.begin(), v.end(), 30);if (pos != v.end()){cout << "找到了" << endl;}else{cout<<"没找到"<

void Test8()
{vector v;v.push_back(10);v.push_back(20);v.push_back(30);v.push_back(40);v.push_back(50);v.insert(v.begin(), 111);vector::iterator pos = find(v.begin(),v.end(), 30);if (pos != v.end()){v.insert(pos, 70);}for (auto e : v){cout << e << " ";}cout << endl;pos = find(v.begin(), v.end(),70);if (pos != v.end()){v.erase(pos);}for (auto e : v){cout << e << " ";}
}

void Test9()
{vector v;v.push_back(1);v.push_back(2);v.push_back(3);vector swapv;swapv.swap(v);cout << "v data:";for (size_t i = 0; i < v.size(); ++i)cout << v[i] << " ";cout << endl;cout << "swapv data:";for (size_t i = 0; i < swapv.size(); ++i)cout << swapv[i] << " ";cout << endl;
}

#include 
#include 
using namespace std;
int main(void)
{vectorarray;array.push_back(100);array.push_back(300);array.push_back(300);array.push_back(300);array.push_back(300);array.push_back(500);vector::iterator itor;for (itor = array.begin(); itor != array.end(); itor++){if (*itor == 300){itor = array.erase(itor);}}for (itor = array.begin(); itor != array.end(); itor++){cout << *itor << " ";}return 0;
}

class Solution {
public:vector> generate(int numRows) {vector> vv;vv.resize(numRows);for(size_t i = 0;i

class Solution {private:const string letterMap[10] = {" "," ","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};string s;vector result;void backtracking(const string&digits,int index){if(index == digits.size()){result.push_back(s);return;}int digit = digits[index]-'0';string letter = letterMap[digit];for(int i = 0;i letterCombinations(string digits) {s.clear();result.clear();if(digits.size()==0){return result;}backtracking(digits,0);return result;}
};

class Solution {
public:int singleNumber(vector& nums) {int ret = 0;for(int i = 0;i<32;i++){int sum = 0;for(auto& e:nums){sum+=(e>>i)&1;}sum%=3;ret+=(sum<

class Solution {
public:vector singleNumber(vector& nums) {vector v;int ret = 0;//整个数组进行异或for(auto e:nums){ret^=e;}//找出不同的二进制位int flag = 0;for(int i = 0;i<32;i++){if((1&(ret>>i)) == 1){flag = i;break;}}//进行分组异或int x1 = 0,x2 = 0;for(auto e: nums){if((1&(e>>flag)) == 1){x1^=e;}else{x2^=e;}}v.push_back(x1);v.push_back(x2);return v;}
};