区间模糊排序---快排思路的应用
1 #include<iostream> 2 #include<ctime> 3 using namespace std; 4 #define max(a,b) (a>b)?a:b 5 #define min(a,b) (a>b)?b:a 6 class Interval 7 { 8 public: 9 double leftbound; 10 double rightbound; 11 Interval(int a, int b) :leftbound(a), rightbound(b){} 12 Interval(Interval &i){ leftbound = i.leftbound; rightbound = i.rightbound; } 13 Interval(){} 14 }; 15 void swap(Interval &a, Interval &b) 16 { 17 Interval temp = a; 18 a = b; 19 b = temp; 20 21 } 22 void display(Interval a[], int begin, int end) 23 { 24 for (int i = begin; i <= end; ++i) 25 cout << "[" << a[i].leftbound << "," << a[i].rightbound << "]" << ","; 26 cout << endl; 27 } 28 void partition(Interval a[], int begin, int end, int &ini, int &ter) //参数ini、ter是引用，是为了作为返回值 29 { 30 31 Interval pivot = a[begin]; //主元区间 32 ini = begin; 33 ter = end + 1; //注意，这里ter从数组外部开始 34 35 int cur = begin + 1; 36 while (cur < ter && cur<end) 37 { 38 if (a[cur].rightbound <= pivot.leftbound && ini<end) //小于主元区间 39 { 40 ++ini; 41 swap(a[cur], a[ini]); 42 ++cur; 43 //cout << "1: "; 44 //display(a, begin, end); 45 } 46 else if (a[cur].leftbound >= pivot.rightbound && ter>begin) //大于主元区间 47 { 48 --ter; 49 swap(a[cur], a[ter]); 50 //cout << "2: "; 51 //display(a, begin, end); 52 53 } 54 else //和主元区间相等， 所以取交集作为新的主元 55 { 56 pivot.leftbound = max(pivot.leftbound, a[cur].leftbound); 57 pivot.rightbound = min(pivot.rightbound, a[cur].rightbound); 58 //cout << "pivot: " << pivot.leftbound<<" ,"<<pivot.rightbound << endl; 59 ++cur; 60 //cout << "3: "; 61 //display(a, begin, end); 62 } 63 } 64 swap(a[ini], a[begin]); //调整 65 66 --ini; 67 //cout << "ini: " << ini <<" "<< "ter: " << ter << endl; 68 //display(a, begin,end); 69 70 71 } 72 void fuzzySortingOfInterval(Interval a[], int begin, int end) 73 { 74 if (begin < end) 75 { 76 int ini, ter; 77 partition(a, begin, end, ini, ter); 78 fuzzySortingOfInterval(a, begin, ini); 79 fuzzySortingOfInterval(a, ter, end); 80 } 81 } 82 int main() 83 { 84 srand(time(NULL)); 85 const int size = 8; 86 Interval a(28508, 31359), b(4712, 30466), c(23267, 30245), d(7134, 8098), e(25400, 26351), f(8079, 29052), g(31163, 31738), h(6346, 24352); 87 Interval array[size] = { a, b, c, d, e, f, g, h }; 88 Interval *array = new Interval[size]; 89 for (int i = 0; i < size; ++i) 90 { 91 array[i].leftbound = rand() % 100; 92 array[i].rightbound = rand() % 100; 93 while (array[i].rightbound < array[i].leftbound) 94 array[i].rightbound = rand() % 100; 95 } 96 display(array, 0, size - 1); 97 fuzzySortingOfInterval(array, 0, size - 1); 98 display(array, 0, size - 1); 99 system("pause"); 100 }
关于算法呢，其实很简单，区间的比较结果有三种：小于，等于（有交集），大于，这里的优化在于，每次有等于情况时都取交集作为新的主元，这样的好处在于：扩大中间等于的区域，减少递归深度。
关于代码呢，这里partition函数我们要返回一个区间，是要返回其左右的数字，而C++只能有一个返回值，因此这里借助了引用返回的技巧来实现，另一方面，我们可以借助STL 的pair类型
pair<int,int>& partition(int begin,int end) { ..... return pair<int,int>(ini,ter); }
调用时 ini=partiton(begin,end).first;ter=partition(begin,end).second;
