归并排序

Posted 2022-09-04 wronin

#include <iostream>
using namespace std;
#define maxn 10005
#define inf 999999
int L[maxn], R[maxn],A[maxn],cnt,n;
void merge(int left, int mid, int right)  //合并
    int len1 = mid - left;
    int len2 = right - mid;
    for (int i = 0; i< len1; i++) L[i] = A[left + i];
    for (int i = 0; i<len2; i++) R[i] = A[mid + i];
    L[len1] = R[len2] = inf;
    int i = 0, j = 0;
    for (int k = left; k < right; k++) 
        cnt++;
        if (L[i] <= R[j]) A[k] = L[i++];
        else A[k] = R[j++];
    

void mergesort(int left, int right) 
    if (left + 1 >= right) return;
    int mid = (left + right) / 2;
    //分解
    mergesort(left, mid);
    mergesort(mid, right);
    //合并
    merge(left, mid, right);

int main() 
    cnt = 0;
    cin >> n;
    for (int i = 0; i < n; i++) cin >> A[i];
    mergesort(0, n);
    for (int i = 0; i<n; i++) cout << A[i] << " ";
    cout << endl;
    return 0;