C++相关闲碎记录(13)-编程知识

1、排序算法

（1）对所有元素排序sort(), stable_sort()

#include "algostuff.hpp"using namespace std;int main() {deque<int> coll;INSERT_ELEMENTS(coll, 1, 9);INSERT_ELEMENTS(coll, 1, 9);PRINT_ELEMENTS(coll, "on entry: ");sort(coll.begin(), coll.end());PRINT_ELEMENTS(coll, "sorted: ");sort(coll.begin(), coll.end(), greater<int>());PRINT_ELEMENTS(coll, "storted > ");return 0;
}
输出：
on entry: 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 
sorted: 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9
storted > 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1

#include "algostuff.hpp"using namespace std;bool lessLength(const string& s1, const string& s2) {return s1.length() < s2.length();
}
int main() {vector<string> coll1 = {"1xxxx", "2x", "3x", "4x", "5xx", "6xxxx", "7xx", "8xxx", "9xx", "10xxx","11", "12", "13", "14xx", "15","16","17"};vector<string> coll2(coll1);PRINT_ELEMENTS(coll1, "on entry: ");sort(coll1.begin(), coll1.end(), lessLength);stable_sort(coll2.begin(), coll2.end(), lessLength);PRINT_ELEMENTS(coll1, "with sort(): \n");PRINT_ELEMENTS(coll2, "with stable_sort(): \n");return 0;
}
输出：
on entry: 1xxxx 2x 3x 4x 5xx 6xxxx 7xx 8xxx 9xx 10xxx 11 12 13 14xx 15 16 17 
with sort():
2x 17 16 15 13 12 11 4x 3x 9xx 7xx 5xx 8xxx 14xx 10xxx 6xxxx 1xxxx
with stable_sort():
2x 3x 4x 11 12 13 15 16 17 5xx 7xx 9xx 8xxx 14xx 1xxxx 6xxxx 10xxx

（2）局部排序partial_sort(), partial_sort()

#include "algostuff.hpp"using namespace std;int main() {deque<int> coll;INSERT_ELEMENTS(coll, 3, 7);INSERT_ELEMENTS(coll, 2, 6);INSERT_ELEMENTS(coll, 1, 5);PRINT_ELEMENTS(coll);partial_sort(coll.begin(), coll.begin()+5,coll.end());PRINT_ELEMENTS(coll);partial_sort(coll.begin(), coll.begin()+5,coll.end(),greater<int>());PRINT_ELEMENTS(coll);partial_sort(coll.begin(), coll.end(),coll.end());PRINT_ELEMENTS(coll);return 0;
}
输出：
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5 
1 2 2 3 3 7 6 5 5 6 4 4 3 4 5
7 6 6 5 5 1 2 2 3 3 4 4 3 4 5
1 2 2 3 3 3 4 4 4 5 5 5 6 6 7

（3）partial_sort_copy()

#include "algostuff.hpp"using namespace std;int main() {deque<int> coll1;vector<int> coll6(6);vector<int> coll30(30);INSERT_ELEMENTS(coll1, 3, 7);INSERT_ELEMENTS(coll1, 2, 6);INSERT_ELEMENTS(coll1, 1, 5);PRINT_ELEMENTS(coll1);vector<int>::const_iterator pos6;pos6 = partial_sort_copy(coll1.cbegin(), coll1.cend(),coll6.begin(), coll6.end());copy(coll6.cbegin(), pos6,ostream_iterator<int>(cout, " "));cout << endl;vector<int>::const_iterator pos30;pos30 = partial_sort_copy(coll1.cbegin(), coll1.cend(),coll30.begin(), coll30.end(),greater<int>());copy(coll30.cbegin(), pos30,ostream_iterator<int>(cout, " "));cout << endl;return 0;
}
输出：
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5 
1 2 2 3 3 3
7 6 6 5 5 5 4 4 4 3 3 3 2 2 1

（4）根据第n个元素排序nth_element()

#include "algostuff.hpp"using namespace std;int main() {deque<int> coll;INSERT_ELEMENTS(coll, 3, 7);INSERT_ELEMENTS(coll, 2, 6);INSERT_ELEMENTS(coll, 1, 5);PRINT_ELEMENTS(coll);nth_element(coll.begin(), coll.begin()+3, coll.end());cout << "the four lowest elements are: ";copy(coll.cbegin(), coll.cbegin()+4, ostream_iterator<int>(cout, " "));cout << endl;nth_element(coll.begin(), coll.end()-4, coll.end());cout << "the four highest elements are: ";copy(coll.cend()-4, coll.cend(), ostream_iterator<int>(cout, " "));cout << endl;nth_element(coll.begin(), coll.begin()+3,coll.end(), greater<int>());cout << "the four highest elements are: ";copy(coll.cbegin(), coll.cbegin()+4,ostream_iterator<int>(cout, " "));cout << endl;return 0;
}
输出：
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5 
the four lowest elements are: 2 1 2 3
the four highest elements are: 5 6 6 7
the four highest elements are: 6 7 6 5

（5）make_heap()、push_heap()、pop_heap()、sort_heap()

#include "algostuff.hpp"using namespace std;int main() {vector<int> coll;INSERT_ELEMENTS(coll, 3, 7);INSERT_ELEMENTS(coll, 5, 9);INSERT_ELEMENTS(coll, 1, 4);PRINT_ELEMENTS(coll, "on entry: ");make_heap(coll.begin(), coll.end());PRINT_ELEMENTS(coll, "after make_heap(): ");pop_heap(coll.begin(), coll.end());coll.pop_back();PRINT_ELEMENTS(coll, "after pop_heap(): ");coll.push_back(17);push_heap(coll.begin(), coll.end());PRINT_ELEMENTS(coll, "after push_heap(): ");sort_heap(coll.begin(), coll.end());PRINT_ELEMENTS(coll, "after sort_heap(): ");return 0;
}
输出：
on entry: 3 4 5 6 7 5 6 7 8 9 1 2 3 4 
after make_heap(): 9 8 6 7 7 5 5 3 6 4 1 2 3 4
after pop_heap(): 8 7 6 7 4 5 5 3 6 4 1 2 3
after push_heap(): 17 7 8 7 4 5 6 3 6 4 1 2 3 5
after sort_heap(): 1 2 3 3 4 4 5 5 6 6 7 7 8 17

调用make_heap之后，元素被排序为9 8 6 7 7 5 5 3 6 4 1 2 3 4

转换为二叉树如下：

2、已排序区间算法

（1）binary_search()

#include "algostuff.hpp"using namespace std;int main() {list<int> coll;INSERT_ELEMENTS(coll, 1, 9);PRINT_ELEMENTS(coll);if(binary_search(coll.begin(), coll.end(), 5)) {cout << "5 is present" << endl;} else {cout << "5 is not present" << endl;}if(binary_search(coll.begin(), coll.end(), 42)) {cout << "42 is present" << endl;} else {cout << "42 is not present" << endl;}return 0;
}
输出：
1 2 3 4 5 6 7 8 9 
5 is present
42 is not present

（2）检查数个元素是否存在includes()

#include "algostuff.hpp"using namespace std;int main() {list<int> coll;vector<int> search;INSERT_ELEMENTS(coll, 1, 9);PRINT_ELEMENTS(coll, "coll: ");search.push_back(3);search.push_back(4);search.push_back(7);PRINT_ELEMENTS(search, "search: ");if(includes(coll.cbegin(), coll.cend(),search.cbegin(), search.cend())) {cout << "all elements of search are also in coll" << endl;} else {cout << "not all elements of search are also in coll" << endl;}return 0;
}
输出：
coll: 1 2 3 4 5 6 7 8 9 
search: 3 4 7
all elements of search are also in coll

（3）查找第一个或者最后一个可能的位置lower_bound()、upper_bound()

#include "algostuff.hpp"using namespace std;int main() {list<int> coll;INSERT_ELEMENTS(coll, 1, 9);INSERT_ELEMENTS(coll, 1, 9);coll.sort();PRINT_ELEMENTS(coll);auto pos1 = lower_bound(coll.cbegin(), coll.cend(), 5);auto pos2 = upper_bound(coll.cbegin(), coll.cend(), 5);cout << "5 could get position "<< distance(coll.cbegin(), pos1) + 1<< " up to " << distance(coll.cbegin(), pos2) + 1<< " without breaking the sorting" << endl;coll.insert(lower_bound(coll.begin(), coll.end(), 3), 3);coll.insert(upper_bound(coll.begin(), coll.end(), 7), 7);PRINT_ELEMENTS(coll);return 0;
}
输出：
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 
5 could get position 9 up to 11 without breaking the sorting
1 1 2 2 3 3 3 4 4 5 5 6 6 7 7 7 8 8 9 9

（4）查找第一个和最后一个可能位置equal_range()

#include "algostuff.hpp"using namespace std;int main() {list<int> coll;INSERT_ELEMENTS(coll, 1, 9);INSERT_ELEMENTS(coll, 1, 9);coll.sort();PRINT_ELEMENTS(coll);pair<list<int>::const_iterator, list<int>::const_iterator> range;range = equal_range(coll.cbegin(), coll.cend(), 5);cout << "5 could get position " << distance(coll.cbegin(), range.first) + 1<< " up to " << distance(coll.cbegin(), range.second) + 1<< " without breaking the sorting" << endl;return 0;
}
输出：
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 
5 could get position 9 up to 11 without breaking the sorting

（5）合并元素merge()

#include "algostuff.hpp"using namespace std;int main() {list<int> coll1;set<int> coll2;INSERT_ELEMENTS(coll1, 1, 6);INSERT_ELEMENTS(coll2, 3, 8);PRINT_ELEMENTS(coll1, "coll1: ");PRINT_ELEMENTS(coll2, "coll2: ");cout << "merged: ";merge(coll1.cbegin(), coll1.cend(),coll2.cbegin(), coll2.cend(),ostream_iterator<int>(cout, " "));cout << endl; return 0;
}
输出：
coll1: 1 2 3 4 5 6 
coll2: 3 4 5 6 7 8
merged: 1 2 3 3 4 4 5 5 6 6 7 8

（6）两个已排序集合的并集set_union(),set_intersection(),set_difference(), set_symmetric_difference()

#include "algostuff.hpp"
using namespace std;int main() {vector<int> c1 = {1, 2, 2, 4, 6, 7, 7, 9};deque<int> c2 = {2, 2, 2, 3, 6, 6, 8, 9};cout << "c1: ";copy(c1.cbegin(), c1.cend(), ostream_iterator<int>(cout, " "));cout << endl;cout << "c2: ";copy(c2.cbegin(), c2.cend(), ostream_iterator<int>(cout, " "));cout << endl << endl;cout << "merged: ";merge(c1.cbegin(), c1.cend(),c2.cbegin(), c2.cend(),ostream_iterator<int>(cout, " "));cout << endl;cout << "set_union: ";set_union(c1.cbegin(), c1.cend(),c2.cbegin(), c2.cend(),ostream_iterator<int>(cout, " "));cout << endl;cout << "set_intersection()";set_intersection(c1.cbegin(), c1.cend(),c2.cbegin(), c2.cend(),ostream_iterator<int>(cout, " "));cout << endl;cout << "set_difference()";set_difference(c1.cbegin(), c1.cend(),c2.cbegin(), c2.cend(),ostream_iterator<int>(cout, " "));cout << endl;cout << "set_symmetric_difference(): ";set_symmetric_difference(c1.cbegin(), c1.cend(),c2.cbegin(), c2.cend(),ostream_iterator<int>(cout, " "));cout << endl;return 0;
}
输出：
c1: 1 2 2 4 6 7 7 9 
c2: 2 2 2 3 6 6 8 9merged: 1 2 2 2 2 2 3 4 6 6 6 7 7 8 9 9
set_union: 1 2 2 2 3 4 6 6 7 7 8 9
set_intersection()2 2 6 9
set_difference()1 4 7 7
set_symmetric_difference(): 1 2 3 4 6 7 7 8

（7）合并连贯之已排序区间inplace_merge()

#include "algostuff.hpp"using namespace std;int main() {list<int> coll;INSERT_ELEMENTS(coll, 1, 7);INSERT_ELEMENTS(coll, 1, 8);PRINT_ELEMENTS(coll);list<int>::iterator pos;pos = find(coll.begin(), coll.end(), 7);++pos;inplace_merge(coll.begin(), pos, coll.end());PRINT_ELEMENTS(coll);return 0;
}
输出：
1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8