算法导论——归并排序

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前面写过选择排序和插入排序，下面是归并排序，如下：

#include<iostream>using namespace std;const int sentry = 999999;void Merge( int ia[], size_t p, size_t q, size_t r){int a1[10], a2[10];size_t len1 = q - p + 1,len2=r-q;for (int i = 0; i <len1; ++i)a1[i] = ia[p+i];a1[len1] = sentry;for (int i = 0; i <len2; ++i)a2[i] = ia[q+i+1];a2[len2] = sentry;int b = 0, c = 0;for (int i = p; i <= r; ++i){if (a1[b] >= a2[c])ia[i] = a2[c++];elseia[i] = a1[b++];}}void Merge_sort( int ia[],size_t p,size_t r){if (p < r ){int q = (p + r) / 2;Merge_sort(ia, p, q);Merge_sort(ia, q + 1, r);Merge(ia, p, q, r);}}int main(){int a[20];int n;cout << "input the size of array:" << endl;cin >> n;for (int i = 0; i < n; ++i)cin >> a[i];//input arrayMerge_sort(a, 0, n-1);for (int i = 0; i < n; ++i)cout << a[i] << " ";cout << endl;return 0;}

写了一下午终于完工。

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