STL中的nth_element()方法的使用 通过调用nth_element(start, start+n, end)
方法可以使第n大元素处于第n位置(从0开始,其位置是下标为
n的元素),并且比这个元素小的元素都排在这个元素之前,比这个元素大的元素都排在这个元素之后,但不能保证他们是有序的,下面是这个方法的具体使用方法.
1 #include <iostream> 2 3 #include <algorithm> 4 5 #include <functional> 6 7 #include <vector> 8 9 using namespace std; 10 11 12 13 int main() 14 15 { 16 17 const int VECTOR_SIZE = 50 ; 18 19 20 21 vector<int> Numbers(VECTOR_SIZE) ; 22 23 24 25 vector<int>::iterator start, end, it ; 26 27 28 29 // Initialize vector Numbers 30 31 for(int i=0;i<50;++i){ 32 33 Numbers[i]=i; 34 35 } 36 37 /*由于赋值时是有序的,下面random_shuffle()方法将这些数据的顺序打乱*/ 38 39 random_shuffle(Numbers.begin(),Numbers.end()); 40 41 42 43 // location of first element of Numbers 44 45 start = Numbers.begin() ; 46 47 48 49 // one past the location last element of Numbers 50 51 end = Numbers.end() ; 52 53 54 55 cout << "Before calling nth_element/n" << endl ; 56 57 58 59 // print content of Numbers 60 61 cout << "Numbers { " ; 62 63 for(it = start; it != end; it++) 64 65 cout << *it << " " ; 66 67 cout << " }/n" << endl ; 68 69 70 71 /* 72 73 * partition the elements by the 8th element, 74 75 *(notice that 0th is the first element) 76 77 */ 78 79 nth_element(start, start+8, end) ; 80 81 82 83 cout << "After calling nth_element/n" << endl ; 84 85 86 87 cout << "Numbers { " ; 88 89 for(it = start; it != end; it++) 90 91 cout << *it << " " ; 92 93 cout << " }/n" << endl ; 94 95 system("pause"); 96 97 }
时间: 2024-10-23 13:00:59