vector的常见用法

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main()
{
	//push_back pop_back clear size操作
	vector<int> a;
	cout << "a.size() " << a.size() << endl;	//0
	for (int i = 0; i < 10; i++) {
		a.push_back(i);
	}
	cout << "after push_back a.size() " << a.size() << endl;	//10
	a.pop_back();
	cout << "after pop_back a.size() " << a.size() << endl;		//9
	a.clear();
	cout << "after clear a.size() " << a.size() << endl;		//0

	//auto迭代器遍历
	vector<int> c;
	for (int i = 1; i <= 5; i++) {
		c.push_back(i);
	}
	cout << "*it" << ' ';
	for (auto it = c.begin(); it != c.end(); it++) {
		cout << *it << ' ';		//1 2 3 4 5
	}
	cout << endl;
	
	//迭代器遍历
	vector<int> d;
	for (int i = 1; i <= 5; i++) {
		d.push_back(i);
	}
	cout << "*k" << ' ';
	for (vector<int>::iterator k = d.begin(); k != d.end(); k++) {
		cout << *k << ' ';		//1 2 3 4 5
	}
	cout << endl;

	//insert erase操作
	vector<int> ins;
	for (int i = 1; i <= 5; i++) {
		ins.push_back(i);
	}
	cout << "before insert: ";
	for (auto i = ins.begin(); i != ins.end(); i++) {
		cout << *i << ' ';		//1 2 3 4 5
	}
	cout << endl;
	cout << "after insert: ";
	ins.insert(ins.begin() + 2, -1);	//ins[i]和*(ins.begin()+i)是等价的
	for (auto i = ins.begin(); i != ins.end(); i++) {
		cout << *i << ' ';		//1 2 -1 3 4 5
	}
	cout << endl;
	ins.erase(ins.begin() + 2);		//erase(it)即删除迭代器为it处的元素
	cout << "after erase: ";
	for (auto i = ins.begin(); i != ins.end(); i++) {
		cout << *i << ' ';		//1 2 3 4 5
	}
	cout << endl;
	ins.erase(ins.begin()+1, ins.begin()+4);	//erase(first,last)即删除左闭右开内所有元素
	cout << "after erase from 1 to 4 : ";
	for (auto i = ins.begin(); i != ins.end(); i++) {
		cout << *i << ' ';			//1 5
	}
	cout << endl;
	
	//reverse
	vector<int>rev;
	for (int i = 1; i <= 5; i++) {
		rev.push_back(i);
	}
	for (auto st = rev.begin(); st != rev.end(); st++) {
		cout << *st << ' ';		//1 2 3 4 5
	}
	cout << endl;
	reverse(rev.begin(),rev.end());
	for (auto st = rev.begin(); st != rev.end(); st++) {
		cout << *st << ' ';		//5 4 3 2 1
	}
	cout << endl;

	//unique erase sort
	//返回去重之后的尾迭代器，仍然为前闭后开，即这个迭代器是去重之后末尾元素的下一个位置。
	//该函数用于离散化，利用迭代器的减法，可计算出去重后的元素个数。
	//unique函数属于STL中比较常用函数，它的功能是元素去重。即”删除”序列中所有相邻的重复元素(只保留一个)。
	//此处的删除，并不是真的删除，而是指重复元素的位置被不重复的元素给占领了。
	//由于它”删除”的是相邻的重复元素，所以在使用unique函数之前，一般都会将目标序列进行排序。
	vector<int> uni;
	for (int i = 1; i <= 5; i++) {
		uni.push_back(i);
		uni.push_back(i);
	}
	for (auto st = uni.begin(); st != uni.end(); st++) {
		cout << *st << ' ';		//1 1 2 2 3 3 4 4 5 5 
	}
	cout << endl;
	int m = unique(uni.begin(), uni.end()) - uni.begin();	//去重后元素的个数
	cout << m << endl;			//5
	
	//把一个vector去重，多余的删掉
	vector<int> uniq;	//初始化uniq
	for (int i = 1; i <= 5; i++) {
		uniq.push_back(i);
		uniq.push_back(i);
	}
	uniq.erase(unique(uniq.begin(), uniq.end()), uniq.end());
	for (auto st = uniq.begin(); st != uniq.end(); st++) {
		cout << *st << ' ';		//1 2 3 4 5
	}
	cout << endl;

	//sort+unique+erase
	vector<int> sor({ 4,4,5,6,7,3,4,3,4,3,5,3,5,5,6,2,2,1,3,4,5,6,6 });
	sort(sor.begin(), sor.end());
	sor.erase(unique(sor.begin(), sor.end()), sor.end());
	for (auto st = sor.begin(); st != sor.end(); st++) {
		cout << *st << ' ';		//1 2 3 4 5 6 7
	}





	//有些场合需要根据一些条件把部分数据输出在同一行，数据中间用空格隔开。
	//由于输出数据的个数是不确定的，为了更方便地处理最后一个满足条件的数据后面
	//不输出额外的空格，可以先用vector记录所有需要输出的数据，然后一次性输出


	return 0;
}