multimap用法

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#include <stdio.h>#include <map>#include <xtree>#include <algorithm>using namespace std;int main(int argc, char** argv){multimap<int, int> mmap;mmap.insert(pair<int, int>(1, 1));mmap.insert(pair<int, int>(1, 2));mmap.insert(pair<int, int>(2, 3));multimap<int, int>::iterator iter = mmap.begin();for (; iter != mmap.end(); ++iter)printf("%d, %d\n", iter->first, iter->second);//查找指定key的元素方法一：multimap<int, int>::iterator iter_lower_bound = mmap.lower_bound(1);multimap<int, int>::iterator iter_upper_bound = mmap.upper_bound(1);for (; iter_lower_bound != iter_upper_bound; iter_lower_bound++)printf("%d, %d\n", iter_lower_bound->first, iter_lower_bound->second);//查找指定key的元素方法二：iter = mmap.find(1);int num = mmap.count(1);int k = 0;for (; iter != mmap.end() && k < num; iter++, k++)printf("%d, %d\n", iter->first, iter->second);//查找指定key的元素方法三：pair<multimap<int, int>::iterator, multimap<int, int>::iterator> p_ret = mmap.equal_range(1);while (p_ret.first != p_ret.second){printf("%d, %d\n", p_ret.first->first, p_ret.first->second);p_ret.first++;}getchar();return 0;}

运行结果为：

1, 11, 22, 31, 11, 21, 11, 21, 11, 2

如果键是降序排列的话

#include <stdio.h>#include <map>#include <xtree>#include <algorithm>using namespace std;struct GreaterComp : public binary_function<const int&, const int&, bool>{result_type operator()(first_argument_type _Left, second_argument_type& _Right){return _Left > _Right;}};int main(int argc, char** argv){multimap<int, int, GreaterComp> mmap;mmap.insert(pair<int, int>(4, 3));mmap.insert(pair<int, int>(4, 3));mmap.insert(pair<int, int>(5, 3));mmap.insert(pair<int, int>(2, 3));mmap.insert(pair<int, int>(1, 1));mmap.insert(pair<int, int>(1, 2));mmap.insert(pair<int, int>(1, 5));mmap.insert(pair<int, int>(2, 3));multimap<int, int, GreaterComp>::iterator iter = mmap.begin();for (; iter != mmap.end(); ++iter)printf("%d, %d\n", iter->first, iter->second);printf("\n");//查找指定key的元素方法一：multimap<int, int, GreaterComp>::iterator iter_lower_bound = mmap.lower_bound(1);multimap<int, int, GreaterComp>::iterator iter_upper_bound = mmap.upper_bound(1);for (; iter_lower_bound != iter_upper_bound; iter_lower_bound++)printf("%d, %d\n", iter_lower_bound->first, iter_lower_bound->second);printf("\n");//查找指定key的元素方法二：iter = mmap.find(1);int num = mmap.count(1);int k = 0;for (; iter != mmap.end() && k < num; iter++, k++)printf("%d, %d\n", iter->first, iter->second);printf("\n");//查找指定key的元素方法三：pair<multimap<int, int, GreaterComp>::iterator, multimap<int, int, GreaterComp>::iterator> p_ret = mmap.equal_range(1);while (p_ret.first != p_ret.second){printf("%d, %d\n", p_ret.first->first, p_ret.first->second);p_ret.first++;}printf("\n");getchar();return 0;}

运行结果为

5, 34, 34, 32, 32, 31, 11, 21, 51, 11, 21, 51, 11, 21, 51, 11, 21, 5

可以发现，操作是没什么不同的

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