为何第一段程序执行后结果会报错，第二段却没事呢？该怎么改？谢谢

//用起泡法对10个数进行由小到大排列
#include <stdio.h>
#define N 10
int main()
{
    int num[N],i,j,smaller;
    printf("input 10 numbers:\n");
    for (i=0;i<N;i++)
        scanf("%d",&num[i]);
    for (j=0;j<N-1;j++)                    //N个数循环N-1趟
        for (i=0;i<N-j;i++)                //第j趟进行N-j次比较
            if (num[i]>num[i+1])
            {    smaller=num[i];
                num[i]=num[i+1];
                num[i+1]=smaller;
            }
    printf("the number from low to high is : \n ");
    for (i=0;i<N;i++)
        printf(" %4d",num[i]);
    printf("\n");
    return 0;
}



//用起泡法对10个数进行由小到大排列
#include <stdio.h>
#define N 10
int main()
{
    int num[N+1],i,j,smaller;
    printf("input numbers:\n");
    for (i=1;i<=N;i++)
        scanf("%d",&num[i]);
    for (j=1;j<N;j++)                        //N个数循环N-1趟
        for (i=1;i<=N-j;i++)                //第j趟进行N-j次比较
            if (num[i]>num[i+1])
            {    smaller=num[i];
                    num[i]=num[i+1];
                    num[i+1]=smaller;
            }
    printf("the number from low to high is : \n ");
    for (i=1;i<=N;i++)
        printf(" %4d",num[i]);
    printf("\n");
    return 0;
}

   for (j=0;j<N-1;j++)                    //N个数循环N-1趟
        for (i=0;i<N-j;i++)                //当j = 0时，会出现num[N-1]和num[N]的比较，而num[N]是不存在的元素
            if (num[i]>num[i+1])
            {    smaller=num[i];
                num[i]=num[i+1];
                num[i+1]=smaller;
            }

哦，谢谢，改为for (i=0;i<N-1-j;i++) 即可