找出字符串中的英语字母并放在数组后面

int main()
{//找出字符串中的英语字母并放在数组后面
    char str[256];
    int i;
    char letter[100],digtal[100];
    int j=0,k=0;
    printf("input:>");
    scanf("%s",str);
    printf("str==:>%s\n",str);
         for ( i = 0; str[i]!='\0'; ++i) {
             if (!((str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z')))
             {
                 digtal[j++] = str[i];//数字
             }
             else
             {
                 letter[k++] = str[i];
             }
         }
//    letter[k] = '\0'; //手动添加结束符
    printf("digtial:%s\n",digtal);
    printf("ouput:>%s \n", strcat(digtal, letter));
    return 0;
}

int main(){
    int n, m;
    int sum=0;
    scanf("%d%d", &n, &m);
    int a[N][N];
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            scanf("%d", &a[i][j]);
        }
    }
//    int aa[][3]={{1,2,3},{4,5,6},{7,8,9}};
    printf("n=%d,m=%d\n",n,m);
    for(int i=0;i<n;i++)
    {
        for(int j=0;j<m;j++)
        {
            printf("%d ",a[i][j]);
        }
        printf("\n");
    }
    for (int i = 0; i <m ; ++i) {
        sum = a[n-1][i] + sum;
        sum=a[0][i]+sum;
    }
    printf("sum= %d",sum);
    return 0;
}