归并排序

归并排序

算法分析

空间效率：$O(n)$
时间效率：$每趟归并时间复杂度为O(n),共需 log_{2}n 趟，时间复杂度为n*log_{2}n$
稳定性：稳定

模板

#include<bits/stdc++.h>

using namespace std;

int n;
const int N = 1e5 + 10;
int a[N], t[N];

void mergeSort(int a[], int l, int r) {
    if (l >= r) return;
    int mid = l + r >> 1;
    mergeSort(a,l,mid);
    mergeSort(a,mid+1,r);
    int i = l, j = mid + 1, k = 0;
    while (i<=mid&&j<=r){
        if(a[i]<=a[j]) t[k++]=a[i++];
        else t[k++]=a[j++];
    }
    while (i<=mid) t[k++]=a[i++];
    while (j<=r) t[k++]=a[j++];
    for (int m = l, n = 0; m <=r ; ++m, ++n) {
        a[m]=t[n];
    }
}

int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; i++) scanf("%d", &a[i]);
    mergeSort(a,0,n-1);
    for (int i = 0; i < n; i++) printf("%d ", a[i]);
    return 0;
}