我們先看一下set_intersection的官方文件模板
template< class InputIt1, class InputIt2, class OutputIt >
OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
InputIt2 first2, InputIt2 last2,
OutputIt d_first );
(1)
template< class InputIt1, class InputIt2,
class OutputIt, class Compare >
OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
InputIt2 first2, InputIt2 last2,
OutputIt d_first, Compare comp );
(2)
Constructs a sorted range beginning at d_first consisting of elements that are found in both sorted ranges [first1, last1) and [first2, last2). The first version expects both input ranges to be sorted with operator<, the second version expects them to be sorted with the given comparison function comp.
所以在intersection前務必對取交集的對象a和b進行sort
std::sort(a.begin(), a.end());
std::sort(b.begin(), b.end());
具體說一下對string取交集的兩種操作
方法1:
//vector<string> words
string int_sec; set_intersection(words[i].begin(),words[i].end(),words[j].begin(),words[j].end(),back_inserter(int_sec));
//得到的string int_sec爲交集的字符
方法2:
char int_sec[100000];
char*int_sec_end=set_intersection(words[i].begin(),words[i].end(),words[j].begin(),words[j].end(),int_sec);
// int_sec_end-int_sec就是個數,並且c[0]到c[int_sec_end-int_sec-1]中存儲的就是那些相同的字符。
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