分治法之归并排序

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分治法：英文名divide and conquer，按照中国的古话就是分而治之，他是将一个大问题divide若干个小问题，再分别对这几个小问题conquer、各个击破，从而解决大问题

归并排序就是用了分治法的思想，不断的将一个数列分为前后两个数列，再进行排序

#include <iostream>using namespace std;///将有二个有序数列a[first...mid]和a[mid...last]合并void MergeArray(int a[], int first, int mid, int last, int temp[]){int i = first, j = mid + 1;int m = mid, n = last;int k = 0;while (i <= m && j <= n){if(a[i] <= a[j])temp[k++] = a[i++];elsetemp[k++] = a[j++];}while(i <= m)temp[k++] = a[i++];while(j <= n)temp[k++] = a[j++];//把temp[]数据装回a[]for(i = 0; i < k; i++)a[first + i] = temp[i];}void Merge(int a[], int first, int last, int temp[]){if (first < last){int mid = (first + last) / 2;Merge(a, first, mid, temp);//左边有序Merge(a, mid + 1, last, temp);//右边有序MergeArray(a, first, mid, last, temp);//合并两个有序数列}}bool MergeSort(int a[], int n){int *p = new int[n];if(p == NULL)return false;Merge(a, 0, n - 1, p);delete[] p;return true;}int main(){int a[10] = {2,6,3,1,0,9,8,7,5,4};int temp[10];Merge(a, 0, 9, temp);for (int i = 0; i < 10; i++)cout<<a[i]<<" ";cout<<endl;return 0;}

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