分治法求解MergeSort

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MergeSort 归并排序，可以理解为将把需要排序的内容分成两部分，排序完之后再合并起来。

void merge(int a[],int b[],int low,int mid,int high){    int s = low , t = mid + 1, k = low;    while(s<=mid&&t<=high)    {        if(a[s] < a[t]){            b[k] = a[s];            s++;        }        else{            b[k] = a[t];            t++;        }        K++;    }    if(s == mid + 1)    {        for(i=k;i<=high;i++)            b[i] = a[t++];    }    else    {        for(i=k;i<=high;i++)            b[i] = a[s++];    }}void MergeSort(int a[],int b[],int low,int high){    if(low<high)    {        int mid = (low + high)/2;        MergeSort(a,b,low,mid);        MergeSort(a,b,mid+1,high);        Merge(a,b,low,mid,high);    }}

MergeSort python实现

def Merge(left,right):    result = []    i,j = 0,0    while(i < len(left) and j < len(right)):        if(left[i] < right[j]):            result.append(left[i])            i += 1        else:            result.append(right[j])            j += 1    while(i < len(left)):        result.append(left[i])        i += 1    while(j < len(right)):        result.append(right[j])        j += 1    return result  def MergeSort(L):    if(len(L) < 2):        return L[:]    else:        mid = int(len(L)/2)        left = MergeSort(L[:mid])        right = MergeSort(L[mid:])        return Merge(left,right)

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