#include<iostream>
using namespace std;
void selcet(int arry[]);
int length;
int main() {
	int a[] = { 1,-17,13,15,-19,10,99,123,124,1000 };
	length = sizeof(a) / sizeof(int);
	for (int i = 0; i < length; i++)
	{
		cout << a[i] << "   ";

	}
	cout << endl << length << "个" << endl;
	selcet(a);
	return 0;
}
void selcet(int a[]) {

	int num , max,i,n;
	for ( i = 0; i < length-1; i++)
	{
		num = i;
		for (n = i+1; n < length; n++)
		{
			if (a[num] < a[n]) {
				num = n;
			}
		}
		max = a[i];
		a[i] = a[num];
		a[num] = max;

	}
	for (int i = 0; i < length; i++)
	{
		cout << a[i] << "   ";

	}
}

完整可运行，

该算法核心：遍历找出最大数值所在的位子与第一个交换，然后从第二个开始重复此操作，以此类推 。