归并排序模板:
- 确定分界点
- 左右递归
- 归并区间
- 将剩余元素传递到数组
注意:
要检查原数组是否含有剩余元素
while (i <= x) temp[k++] = a[i++];
while (j <= r) temp[k++] = a[j++];
#include <iostream>
using namespace std;
const int N = 1e5 + 10;
int a[N], temp[N] ;
void merge_sort(int a[], int l, int r)
{
if (l >= r) return;
int x = l + r >> 1;
merge_sort(a, l, x);
merge_sort(a, x + 1, r);
int i = l, j = x + 1;
int k = 0;//k是temp数组的指针
while (i <= x && j <= r)
if (a[i] <= a[j]) temp[k++] = a[i++];
else temp[k++] = a[j++];
while (i <= x) temp[k++] = a[i++];
while (j <= r) temp[k++] = a[j++];
for (int k = 0, i = l; i <= r; i++,k++ ) a[i] = temp[k];
}
int main()
{
int n;
cin >> n;
for (int i = 0; i < n; i++) cin >> a[i];
merge_sort(a, 0, n - 1);
for (int i = 0; i < n; i++)
printf("%d ", a[i]);
return 0;
}