归并排序（基于顺序容器vector_递归；基于数组array_递归_非递归）

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代码1：基于顺序容器vector

  1 /*  2  * FILE: merge_sort_vector.cpp  3  * ---------------------------  4  * DATE: 20170818  5  * 归并排序，使用顺序容器vector  6  *  7  */  8   9 #include <iostream> 10 #include <vector> 11  12 void merge(std::vector<int> &v, std::vector<int> &v1, std::vector<int> &v2); 13  14 /* recursive 递归 一分两半 */ 15 void sort(std::vector<int> &v) 16 { 17         int n = v.size(); 18         if(n <= 1) 19                 return; 20         std::vector<int> v1; 21         std::vector<int> v2; 22         for(int i = 0; i < n; i++) 23         { 24                 if(i < n/2) 25                         v1.push_back(v[i]); 26                 else     27                         v2.push_back(v[i]); 28         }                29         sort(v1); 30         sort(v2); 31         v.clear(); 32         merge(v, v1, v2); 33 }        34  35 /* 合并 排序 */ 36 void merge(std::vector<int> &v, std::vector<int> &v1, std::vector<int> &v2) 37 { 38         int n1 = v1.size(); 39         int n2 = v2.size(); 40         int p1 = 0, p2 = 0; 41         while(p1 < n1 || p2 < n2) 42         { 43                 if(p1 >= n1) 44                         v.push_back(v2[p2++]); 45                 else if(p2 >= n2) 46                         v.push_back(v1[p1++]); 47                 else if(v1[p1] < v2[p2]) 48                         v.push_back(v1[p1++]); 49                 else 50                         v.push_back(v2[p2++]); 51         } 52 } 53  54 /* 使用vector的迭代器 打印输出 */ 55 void display(std::vector<int> &v) 56 { 57         for(std::vector<int>::iterator iter = v.begin(); iter != v.end(); iter++) 58                 std::cout<< *iter <<"  "; 59         std::cout<< std::endl; 60 } 61  62 int main() 63 { 64         int a[] = {3,4,2,1,7,5,8,9,0,6}; 65         int length = sizeof(a) / sizeof(int); 66         std::vector<int> vec(a, a+length-1); 67         sort(vec); 68         display(vec); 69         return 0; 70 }

代码2：基于数组（递归法、非递归）

  1 /*  2  * FIEL: merge_sort.cpp  3  * --------------------  4  * DATE: 20170818  5  * 归并排序：先一分两半，分别进行排序；再合并两个已排好序的数组  6  *  7  */  8   9 #include <iostream> 10  11 /*  12  * merge two sorted sub-array 13  * 合并两个已排好序的数组  14  */ 15 void merge(int a[], int result[], int begin, int middle, int length) 16 { 17         //int result[length]; 18         int left = begin, right = middle; 19         int index = begin; 20         while(left < middle || right < length) 21         { 22                 if(left >= middle) 23                 { 24                         result[index++] = a[right++]; 25                         //right++; 26                 } 27                 else if(right >= length) 28                 { 29                         result[index++] = a[left++]; 30                         //left++; 31                 } 32                 else if(a[left] < a[right]) 33                 { 34                         result[index++] = a[left++]; 35                         //left++; 36                 } 37                 else    // a[left] >= a[right] 38                 { 39                         result[index++] = a[right++]; 40                         //right++; 41                 } 42                 //index++; 43         } 44         for(int i = begin; i < length; i++) 45                 a[i] = result[i]; 46 } 47  48 /* recursive 递归 */ 49 void mergeSort_recursive(int a[], int temp[], int begin, int length) 50 { 51         if(length - begin <= 1) 52                 return; 53         int middle = (begin + length) / 2; 54         mergeSort_recursive(a, temp, begin, middle); 55         mergeSort_recursive(a, temp, middle, length); 56         merge(a, temp, begin, middle, length); 57  58 } 59  60 void mergeSort_recursive(int a[], int length) 61 { 62         int *temp = new int[length]; 63         mergeSort_recursive(a, temp, 0, length); 64         delete []temp; 65 } 66  67 /* non_recursive 非递归 */ 68 void mergeSort(int a[], int length) 69 { 70         int *temp = new int[length]; 71         for(int step = 1; step < length; step = step * 2) 72         { 73                 for(int left = 0; left < length; left = left + 2 * step) 74                 { 75                         int middle = std::min(left + step, length); 76                         int right = std::min(left + 2 * step, length); 77                         merge(a, temp, left, middle, right); 78                 } 79         } 80         delete []temp; 81 } 82  83 int main(int argc, char *argv[]) 84 { 85         int a[] = {3,4,2,1,7,5,8,9,0,6}; 86         int length = sizeof(a) / sizeof(int); 87         std::cout<< "递归法："; 88         mergeSort_recursive(a, length); //递归法 89         for(int i = 0; i < length; i++) 90                 std::cout<< a[i] << "  "; 91         std::cout<< std::endl; 92  93         int b[] = {3,4,2,1,7,5,8,9,0,6}; 94         mergeSort(b, length);   //非递归 95         std::cout<< "非递归："; 96         for(int i = 0; i < length; i++) 97                 std::cout<< b[i] << "  "; 98         std::cout<< std::endl; 99         return 0;100 }

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