歸併排序程式碼

MergeSort.hpp

//
// Created by Administrator on 2021/7/28.
//

#ifndef C__TEST01_MERGESORT_HPP
#define C__TEST01_MERGESORT_HPP
#include <vector>
#include <iostream>
using namespace std;

class MergeSort {
public:
    MergeSort(vector<int> An);
    void process(vector<int> &A, int L, int R);
    void merge(vector<int> &A, int L, int mid, int R);
private:
    vector<int> A;
};

MergeSort::MergeSort(vector<int> An) :
A(An){
    A.resize(An.size());
}

void MergeSort::process(vector<int> &A, int L, int R) {
    if(L == R){
        return;
    }
    int mid = L + ((R-L) >> 1);
    process(A, L, mid);
    process(A, mid+1, R);
    merge(A, L, mid, R);
}

void MergeSort::merge(vector<int> &A, int L, int mid, int R) {
    vector<int> arr(R-L+1);
    int i = 0;
    int p1 = L;
    int p2 = mid+1;
    while(p1 <= mid && p2 <= R){
        arr[i++] = A[p1] <= A[p2]?A[p1++]:A[p2++];
    }
    while(p1 <= mid){
        arr[i++] = A[p1++];
    }
    while(p2 <= R){
        arr[i++] = A[p2++];
    }
    for(i = 0; i<arr.size(); ++i){
        A[L+i] = arr[i];
    }
}
#endif //C__TEST01_MERGESORT_HPP