【算法】归并排序

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好好学习，天天向上...ORZ

===========我是一条咸鱼的分割线==============

思路：

　　先递归分割，然后归并排序

代码：

　　

#include <iostream>

using namespace std;

void merge(int* str1, int s, int m, int e) {
    int * p = new int[e - s + 1];
    int count = 0;
    for (int i = s, j = m + 1; i <= m || j <= e;) {
        if (i <= m && j <= e && str1[i] >= str1[j]) {
            p[count++] = str1[j];
            j++;
        }
        else if (i <= m && j <= e && str1[i] < str1[j]) {
            p[count++] = str1[i];
            i++;
        }
        else if (i > m && j <= e) {
            p[count++] = str1[j];
            j++;
        }
        else if (i <= m && j > e) {
            p[count++] = str1[i];
            i++;
        }
    }

    for (int i = s, j = 0; i <= e && j < count; i++, j++)
        str1[i] = p[j];

    delete p;
}

void mysort(int* num, int a, int b) {

    if (a >= b)return;

    int mid = (a + b) / 2;
    if (b > a + 1) {
        mysort(num, a, mid);
        mysort(num, mid + 1, b);
    }
    merge(num, a, mid, b);
}


int main() {
    int* num = new int[10];
    int count = 10;

    for (int i = 0; i < 10; i++) {
        cin >> num[i];
    }

    mysort(num, 0, 9);

    for (int i = 0; i < count; i++)
        cout << num[i] << " ";
    cout << endl;

    system("pause");
    return 0;
}

参考：http://www.cnblogs.com/skywang12345/p/3602369.html