清除字符串string中的空格

1、只清除字符串首尾的空格

方法一：調用string的成員函數來進行操作

#include<iostream>
#include<string>
#include<sstream>
using namespace std;

int main()
{
	//str字符串首尾各有兩個空格。
	string str = "  hello this is just a test.  ";
	int len1 = str.length();

	auto s1 = str.find_first_not_of(' ');
	string res = str.substr(s1);
	auto s2 = res.find_last_not_of(' ');
	// erase默認會從所給位置開始一直刪除到字符串的末尾
	res.erase(s2+1);
	int len2 = res.length();

	cout << "len1= " << len1 << " \nlen2= " << len2 << " \nres= " << res << endl;
	
	system("pause");
	return 0;
}

方法二

#include<iostream>
#include<string>
#include<sstream>
using namespace std;

int main()
{
	//str字符串首尾各有兩個空格。
	string str = "  hello this is just a test.  ";
	int len1 = str.length();

	int i = 0;
	for (; i < len1; ++i)
	{
		if (str[i] != ' ')
			break;
	}
	str.erase(0, i);

	i = str.length() - 1;
	for (; i >= 0; --i)
	{
		if (str[i] != ' ')
			break;
	}
	str.erase(i + 1);
	int len2 = str.length();

	cout << "len1= " << len1 << " \nlen2= " << len2 << " \nstr= " << str << endl;
	
	system("pause");
	return 0;
}

---

2、清除字符串中所有的空格

方法一

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

int main()
{
	//str字符串首尾各有兩個空格。
	string str = "  hello this is just a test.  ";
	string tmp;
	vector<string> res;
	bool flag = false;

	for (int i = 0; i < str.length(); ++i)
	{
		if (str[i] != ' ')
		{
			tmp += str[i];
			flag = true;
		}
		else
		{
			if (flag)
			{
				res.push_back(tmp);
				tmp.clear();
				flag = false;
			}
		
		}
	}
	for (auto &s : res)
		cout << s << endl;
	
	system("pause");
	return 0;
}

方法二：使用sstream

#include<iostream>
#include<string>
#include<sstream>
#include<vector>
using namespace std;

int main()
{
	//str字符串首尾各有兩個空格。
	string str = "  hello this is just a test.  ";
	string tmp;
	vector<string> res;
	
	istringstream iss(str);
	while (iss >> tmp)
	{
		res.push_back(tmp);
	}

	for (auto &s : res)
		cout << s << endl;
	
	system("pause");
	return 0;
}