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一、vector

   1.介绍

#include<iostream>
#include<vector>
using namespace std;int main()
{//构造vector<int> v1;vector<int> v2(10, 1);vector<int> v3(v2.begin(), v2.end());string str = "hello";vector<int> v4(str.begin(), str.end());vector<int> v5(v4);//遍历for (size_t i = 0; i < v3.size(); i++)cout << v3[i] << " ";cout << endl;vector<int>::iterator it = v4.begin();while (it != v4.end()){cout << *it << " ";it++;}cout << endl;for (auto e : v5)cout << e << " ";cout << endl;return 0;
}

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    3. 测试vector的默认扩容机制

#include<iostream>
#include<vector>
using namespace std;int main()
{size_t sz;vector<int> v;sz = v.capacity();cout << "making v grow:\n";for (int i = 0; i < 100; ++i){v.push_back(i);if (sz != v.capacity()){sz = v.capacity();cout << "capacity changed: " << sz << '\n';}}return 0;
}

vs下使用的STL基本是按照1.5倍方式扩容     

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    4.reserve 、resize

#include<iostream>
#include<vector>
using namespace std;int main()
{vector<int> v;//v.reserve(100);  // size = 0    capacity 100v.resize(100);     // size = 100  capacity 100for (size_t i = 0; i < 100; i++){v[i] = i;}for (auto e : v){cout << e << " ";}cout << endl;return 0;
}

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    5.push_back 、insert 、find 、erase

#include<iostream>
#include<vector>
using namespace std;int main()
{vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);for (auto e : v){cout << e << " ";}cout << endl;v.insert(v.begin(), 0);for (auto e : v){cout << e << " ";}cout << endl;auto it = find(v.begin(), v.end(), 3);if (it != v.end()){v.insert(it, 30);}for (auto e : v){cout << e << " ";}cout << endl;it = find(v.begin(), v.end(), 3);if (it != v.end()){v.erase(it);}for (auto e : v){cout << e << " ";}cout << endl;return 0;
}

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    6.size 、capacity

#include<iostream>
#include<vector>
using namespace std;int main()
{vector<int> v(6,8);cout << v.size() << endl;cout << v.capacity() << endl;v.clear();cout << v.size() << endl;cout << v.capacity() << endl;v.shrink_to_fit();cout << v.size() << endl;cout << v.capacity() << endl;return 0;
}

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二、题目

    1.第一题

//力扣的格式
class Solution {
public:int singleNumber(vector<int>& nums) {int val = 0;for(auto e : nums){val ^= e;}return val;}
};

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    2.第二题

//力扣的格式
class Solution {
public:vector<vector<int>> generate(int numRows) {vector<vector<int>> vv;vv.resize(numRows);for(size_t i = 0;i<vv.size();i++){vv[i].resize(i+1,0);vv[i][0]=vv[i][vv[i].size()-1]=1;}for(size_t i = 0;i<vv.size();i++)for(size_t j = 0;j<vv[i].size();j++)if(vv[i][j]==0)vv[i][j]=vv[i-1][j]+vv[i-1][j-1];return vv;}
};

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总结

        以上就是今天要讲的内容，本文仅仅简单介绍了c++的基础知识。