比较两个向量 C++
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Compare two vectors C++
提问by Adrian
I was wondering is there any function to compare 2 string vectors to return the number of different(or the same) elements? Or i have to iterate over both of them and test item by item.
Thanks.
我想知道是否有任何函数可以比较 2 个字符串向量以返回不同（或相同）元素的数量？或者我必须遍历它们并逐项测试。
谢谢。
回答by Erik
std::sort(v1.begin(), v1.end());
std::sort(v2.begin(), v2.end());
std::vector<string> v3;
std::set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), std::back_inserter(v3));
Or, if you don't want to sort:
或者，如果您不想排序：
std::set<string> s1(v1.begin(), v1.end());
std::set<string> s2(v2.begin(), v2.end());
std::vector<string> v3;
std::set_intersection(s1.begin(), s1.end(), s2.begin(), s2.end(), std::back_inserter(v3));
You may want to use a multiset if there could be duplicates in a vector.
如果向量中可能存在重复项，您可能需要使用多重集。
回答by JaredPar
I don't know of an existing function but writing one yourself shouldn't be too much trouble.
我不知道现有的函数，但自己编写一个函数应该不会太麻烦。
int compare(const vector<string>& left, const vector<string>& right) {
auto leftIt = left.begin();
auto rightIt = right.begin();
auto diff = 0;
while (leftIt != left.end() && rightIt != right.end()) {
if (*leftIt != *rightIt) {
diff++;
}
leftIt++;
rightIt++;
}
// Account for different length vector instances
if (0 == diff && (leftIt != left.end() || rightIt != right.end())) {
diff = 1;
}
return diff;
}
Notes
笔记
- Omitted
std::prefix for brevity - This function needs to be updated if it should handle
vector<string>instances of different lengths
std::为简洁起见省略前缀- 如果它应该处理
vector<string>不同长度的实例，则需要更新此函数
回答by Morten Kristensen
Have a look at set_difference()and set_intersection(). In both cases you need to have your containers sorted beforehand.
看看set_difference()和set_intersection()。在这两种情况下，您都需要事先对容器进行分类。
