insert sort--插入排序

#include <stdio.h>

void show_string(int num[], int length)
{
    unsigned i;
    for(i = 0; i < length; i++) {
        printf("%3d",num[i]);
    }
    printf("\n");
}

int insert_sort(int num[], int length)
{
    unsigned i,j,key;

    if(length < 0)
        return -1;

    for(j = 1; j < length; j++) {
        key = num[j];
        i = j-1;

        while(i >= 0 && key < num[i]) {
            num[i+1] = num[i];
            i--;
        }
        num[i+1] = key;
    }
}

int main()
{
    int a[5] = {1,6,8,2,5};
    unsigned length = sizeof(a)/sizeof(a[0]);

    show_string(a, length);
    insert_sort(a,length);
    show_string(a, length);
}

复杂度：T(n)=n2 或 T(n)=n