C++ Split string into vector<string> by space

在C++中，我们有时候需要拆分字符串，比如字符串string str = "dog cat cat dog"想以空格区分拆成四个单词，Java中实在太方便了，直接String[] v = str.split(" ");就搞定了，而c++中没有这么方便的实现，但也有很多的方法能实现这个功能，下面列出五种常用的实现的方法，请根据需要选择，个人觉得前三种使用起来比较方便，参见代码如下：

#include <vector>
#include <iostream>
#include <string>
#include <sstream>

string str = "dog cat cat dog";
istringstream in(str);
vector<string> v;

// Method 1
string t;
while (in >> t) {
v.push_back(t);
}

// Method 2
// #include <iterator>
copy(istream_iterator<string>(in), istream_iterator<string>(), back_inserter(v));

// Method 3
string t;
while (getline(in, t, ' ')) {
v.push_back(t);
}

// Method 4
string str2 = str;
while (str2.find(" ") != string::npos) {
int found = str2.find(" ");
v.push_back(str2.substr(0, found));
str2 = str2.substr(found + 1);
}
v.push_back(str2);

// Method 5
// #include <stdio.h>
// #include <stdlib.h>
// #include <string.h>
char *dup = strdup(str.c_str());
char *token = strtok(dup, " ");
while (token != NULL) {
v.push_back(string(token));
token = strtok(NULL, " ");
}
free(dup);