Attention.txt

1. 万能头文件
#include<bits/stdc++.h>

2.保留小数点后3位
#include <iomanip>
cout << setiosflags(ios::fixed) << setprecision(4) << x << endl;

3.在vector中删除某个元素
q.erase(q.begin() + t);
for (vector<int>::iterator it = q.begin(); it != q.end(); )
{
	if (*it == i)
		it = q.erase(it); //不能写成arr.erase(it);
	else
		++it;		
}

4.在vector中查找是否存在某个元素
vector<int>::iterator result = find(q.begin(), q.end(), i);
if (result != q.end())
{
	******
}

5.memset设置为-1
memset(vis, 0xff, sizeof(vis));

6.输出数组中最大的元素
#include <algorithm>
cout << * max_element(maxn, maxn + n) << endl;

7.字符串string的查询


8.结构体的定义与赋值
struct ways
{
	int sou, des, day;
	ways(int s, int d, int dd) : sou(s), des(d), day(dd) {};

};

9.数字int status转化为字符串char temp[10]
sprintf(temp, "%09d", status);

10.结构体内运算符重载
struct node
{
	int des, depth;
	friend bool operator<(const node &n, const node &n1)
	{
		return n.depth > n1.depth;
	}
	node(){}
	node(int d, int de) :des(d), depth(de) {}
};

11.string的常用操作
string str;
str.find("/../") != -1;
str.rfind('/', pos);
str.erase(start, length);

12.vector排序
sort(vec.begin(), vec.end(), cmp);

13.结构体比较大小
bool operator<(const trading& t1) const
	{
		if (t == 's')
			return price > t1.price;
		else
			return price < t1.price;
	}

14.大小写转换
for (int i = 0; i < s.size(); i++)
			s1 += tolower(s[i]);

15.map的遍历输出
map<char, int>::iterator it;
		for (it = ori.begin(); it != ori.end(); it++)
		{
			cout << " -" << it->first;
			if (it->second == 2)
				cout << " " << st[it->first];
		}