Merge sort

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pseudocode：

MERGE-SORTA[1 . . n]1.If n= 1, done.2.Recursively sort A[ 1 . . ⎡n/2⎤]and A[ ⎡n/2⎤+1 . . n ] .3.“Merge”the 2sorted lists.

C++:

const int N = 100;void merge(int * a,int lhs,int mid,int rhs) {    int b[N];    int p1 = lhs;    //数组1下标    int p2 = mid + 1; //数组2下标    int p3 = 0;  //b[] 下标    while (p1 <= mid && p2 <= rhs) {        if (a[p1] <= a[p2]) {            b[p3] = a[p1];            ++p1;            ++p3;        }        else {            b[p3] = a[p2];            ++p2;            ++p3;        }    }    if (p1 <= mid) {        for (;  p1<= mid; ++p1) {            b[p3] = a[p1];            ++p3;        }    }    else {        for (; p2 <= rhs; ++p2) {            b[p3] = a[p2];            ++p3;        }    }    for (int i = lhs, j = 0 ; i <= rhs; ++i,++j) {        a[i] = b[j];    }}void MergeSort(int * a,int lhs,int rhs) {    if (lhs < rhs) {        int mid = (lhs + rhs) / 2;        MergeSort(a, lhs, mid);        MergeSort(a, mid + 1, rhs);        merge(a, lhs, mid , rhs);    }}

Text：

#include<iostream>const int N = 100;void merge(int * a,int lhs,int mid,int rhs) {    int b[N];    int p1 = lhs;    //数组1下标    int p2 = mid + 1; //数组2下标    int p3 = 0;  //b[] 下标    while (p1 <= mid && p2 <= rhs) {        if (a[p1] <= a[p2]) {            b[p3] = a[p1];            ++p1;            ++p3;        }        else {            b[p3] = a[p2];            ++p2;            ++p3;        }    }    if (p1 <= mid) {        for (;  p1<= mid; ++p1) {            b[p3] = a[p1];            ++p3;        }    }    else {        for (; p2 <= rhs; ++p2) {            b[p3] = a[p2];            ++p3;        }    }    for (int i = lhs, j = 0 ; i <= rhs; ++i,++j) {        a[i] = b[j];    }}void MergeSort(int * a,int lhs,int rhs) {    if (lhs < rhs) {        int mid = (lhs + rhs) / 2;        MergeSort(a, lhs, mid);        MergeSort(a, mid + 1, rhs);        merge(a, lhs, mid , rhs);    }}int main() {    int a[11] = { 10,9,8,7,6,5,4,3,2,1,0 };    MergeSort(a, 0,10);    for (auto c : a) {        std::cout << c << std::endl;    }    return 0;}

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