【笔记】Stanford OpenCourse—CS106A：Programming Methodology—006
Assignment 2: Simple Java Programs
Problem 1: Brick Pyramids
这题要求画个图1所示的类似金字塔的东东，主要是使用getWidth()，和getHeitht().
图 1
1
/*
File pyramid.java
2
* this program draws a pyramid
3
* Programming exercise 1 cs106a stanford:
4
* Assignment #2: Simple Java Programs
5
* Write a GraphicsProgram subclass that draws a pyramid consisting of bricks
6
arranged in horizontal rows, so that the number of bricks in each row decreases by
7
one as you move up the pyramid
8
The pyramid should be centered at the bottom of the window and should use
9
constants for the following parameters:
10
BRICK_WIDTH The width of each brick (30 pixels)
11
BRICK_HEIGHT The height of each brick (12 pixels)
12
BRICKS_IN_BASE The number of bricks in the base (14)
13
The numbers in parentheses show the values for this diagram, but you must be able
14
to change those values in your program.
15
*/
16
17
import
acm.program.
*
;
18
import
acm.graphics.
*
;
19
20
21
public
class
Pyramid
extends
GraphicsProgram {
22
23
private
static
final
int
BRICK_WIDTH
=
30
;
//
The width of each brick (30 pixels)
24
private
static
final
int
BRICK_HEIGHT
=
12
;
//
The height of each brick (12 pixels)
25
private
static
final
int
BRICKS_IN_BASE
=
14
;
//
The number of bricks in the base (14)
26
27
28
public
void
run() {
29
drawPyramid();
30
}
31
32
private
void
drawBrick(
double
x,
double
y) {
33
GRect brick
=
new
GRect( x, y, BRICK_WIDTH,BRICK_HEIGHT);;
34
add (brick);
35
36
}
37
38
private
void
drawRowOfBricks(
double
x,
double
y,
int
n){
39
for
(
int
i
=
0
; i
<
n; i
++
){
40
41
drawBrick(x
+
i
*
BRICK_WIDTH,y);
42
}
43
}
44
45
private
void
drawCenteredRowOfBricks(
double
y,
int
n) {
46
double
x
=
getWidth()
/
2
-
n
*
BRICK_WIDTH
/
2
;
47
drawRowOfBricks(x, y, n);
48
}
49
50
private
void
drawPyramid(){
51
double
y
=
getHeight();
52
for
(
int
i
=
BRICKS_IN_BASE; i
>
0
; i
--
) {
53
y
-=
BRICK_HEIGHT;
54
drawCenteredRowOfBricks(y, i);
55
}
56
}
57
}
Proble 2：Rainbow
这题要画个图2所示的彩虹。
图 2
1
/**
File: Rainbow.java
2
* ------------------
3
* This program is a stub for the Rainbow problem, which displays
4
* a rainbow by adding consecutively smaller circles to the canvas.
5
*/
6
7
import
acm.program.
*
;
8
import
acm.graphics.
*
;
9
import
java.awt.
*
;
10
11
public
class
Rainbow
extends
GraphicsProgram {
12
13
public
void
run() {
14
drawSky();
15
drawRainbow();
16
}
17
18
private
void
drawSky() {
19
int
skyWidth
=
getWidth();
20
int
skyHeight
=
getHeight();
21
GRect sky
=
new
GRect(
0
,
0
, skyWidth, skyHeight);
22
sky.setColor(Color.CYAN);
23
sky.setFillColor(Color.CYAN);
24
sky.setFilled(
true
);
25
add(sky);
26
}
27
28
private
void
drawRainbow() {
29
Color bandColor
=
Color.RED;
30
for
(
int
i
=
0
; i
<
7
; i
++
) {
31
switch
(i) {
32
case
1
: bandColor
=
Color.ORANGE;
break
;
33
case
2
: bandColor
=
Color.YELLOW;
break
;
34
case
3
: bandColor
=
Color.GREEN;
break
;
35
case
4
: bandColor
=
Color.BLUE;
break
;
36
case
5
: bandColor
=
Color.MAGENTA;
break
;
37
case
6
: bandColor
=
Color.CYAN;
break
;
38
}
39
40
double
offset
=
20
*
i;
41
double
bandDiameter
=
1.5
*
getWidth()
-
(offset
*
2
);
42
double
bandX
=
(getWidth()
-
bandDiameter)
/
2
;
43
double
bandY
=
getHeight()
/
10
+
offset;
44
45
GOval band
=
new
GOval(bandX, bandY, bandDiameter, bandDiameter);
46
band.setColor(bandColor);
47
band.setFillColor(bandColor);
48
band.setFilled(
true
);
49
add(band);
50
}
51
}
52
}
Problem 3：Graphics Hierarchy
如图3，画个结构图。
图 3
1
/*
2
* File: GraphicsHierarchy.java
3
* ----------------------------
4
* This program is a stub for the GraphicsHierarchy problem, which
5
* draws a partial diagram of the acm.graphics hierarchy.
6
*/
7
8
import
acm.program.
*
;
9
import
acm.graphics.
*
;
10
11
public
class
GraphicsHierarchy
extends
GraphicsProgram {
12
private
static
final
double
BOX_HEIGHT
=
50
;
13
private
static
final
double
BOX_WIDTH
=
100
;
14
15
public
void
run() {
16
drawRowOne();
17
drawRowTwo();
18
}
19
20
private
void
drawRowOne() {
21
double
centerX
=
getWidth()
/
2
;
22
double
centerY
=
getHeight()
/
4
;
23
24
drawBox(centerX, centerY,
"
GObject
"
);
25
}
26
27
private
void
drawRowTwo() {
28
String boxType
=
"
GLabel
"
;
29
for
(
int
i
=
1
; i
<
5
; i
++
) {
30
double
centerY
=
getHeight()
*
2
/
3
;
31
double
centerX
=
getWidth()
/
5
*
i;
32
33
switch
(i) {
34
case
1
:
break
;
35
case
2
: boxType
=
"
GLine
"
;
break
;
36
case
3
: boxType
=
"
GOval
"
;
break
;
37
case
4
: boxType
=
"
GRect
"
;
break
;
38
}
39
40
drawBox(centerX, centerY, boxType);
41
drawLineToRowOne(centerX, centerY);
42
}
43
}
44
45
private
void
drawBox(
double
centerX,
double
centerY, String boxType) {
46
double
boxX
=
centerX
-
BOX_WIDTH
/
2
;
47
double
boxY
=
centerY
-
BOX_HEIGHT
/
2
;
48
GRect box
=
new
GRect(boxX, boxY, BOX_WIDTH, BOX_HEIGHT);
49
add(box);
50
51
GLabel label
=
new
GLabel(boxType);
52
label.setFont(
"
Palatino-Bold-12
"
);
53
double
labelX
=
centerX
-
label.getWidth()
/
2
;
54
double
labelY
=
centerY
+
label.getAscent()
/
2
;
55
add(label, labelX, labelY);
56
57
}
58
59
private
void
drawLineToRowOne(
double
centerX,
double
centerY) {
60
//
the middle point of base line boxes
61
double
x0
=
centerX;
62
double
y0
=
centerY
-
BOX_HEIGHT
/
2
;
63
//
the middle point of top line
64
double
x1
=
getWidth()
/
2
;
65
double
y1
=
getHeight()
/
4
+
BOX_HEIGHT
/
2
;
66
GLine line
=
new
GLine(x0, y0, x1, y1);
67
add(line);
68
}
69
70
}
Problem :4：Quadratic Formula
一元二次方程求根公式。
1
/*
2
* File: Quadratic.java
3
* --------------------
4
* This program is a stub for the Quadratic problem, which finds the
5
* roots of the quadratic equation.
6
*/
7
8
import
acm.program.
*
;
9
10
public
class
Quadratic
extends
ConsoleProgram {
11
12
public
void
run() {
13
println(
"
Enter coefficients for the quadratic equation:
"
);
14
double
a
=
readDouble(
"
a:
"
);
15
double
b
=
readDouble(
"
b:
"
);
16
double
c
=
readDouble(
"
c:
"
);
17
18
double
delta
=
Math.sqrt(b
*
b
-
4
*
a
*
c);
19
if
(delta
>=
0
){
20
println(
"
The first solution is
"
+
(
-
b
+
delta)
/
(
2
*
a));
21
println(
"
The first solution is
"
+
(
-
b
-
delta)
/
(
2
*
a));
22
}
else
{
23
println(
"
The equation has no real solutions.
"
);
24
}
25
}
26
27
}
Problem 5：Determining the Range
排排坐，输入一系列数，选出最大的和最小的。这里用了2中方法实现。
1
/*
2
* File: FindRange.java
3
* --------------------
4
* This program is a stub for the FindRange problem, which finds the
5
* smallest and largest values in a list of integers.
6
*/
7
8
import
acm.program.
*
;
9
10
/*
11
public class FindRange extends ConsoleProgram {
12
13
public static final int SENTINEL = 0;
14
15
public void run() {
16
println ("This program finds the largest and smallest numbers.");
17
18
int largestNumber = Integer.MIN_VALUE;
19
int smallestNumber = Integer.MAX_VALUE;
20
21
while (true) {
22
int x = readInt("? ");
23
if (x == SENTINEL) break;
24
25
if (x > largestNumber) largestNumber = x;
26
if (x < smallestNumber) smallestNumber = x;
27
}
28
29
if (largestNumber >= smallestNumber) {
30
println("smallest: " + smallestNumber);
31
println("largest: " + largestNumber);
32
} else {
33
println("No values given.");
34
}
35
}
36
37
}
38
*/
39
40
public
class
FindRange
extends
ConsoleProgram{
41
42
/*
Specifies the value of the sentinel
*/
43
private
static
final
int
SENTINEL
=
0
;
44
45
public
void
run(){
46
intro();
47
enterValue();
48
}
49
50
51
private
void
intro() {
52
println(
"
This program determines the maximum and minimum values.
"
);
53
println(
"
Enter values, one per line, using
"
+
SENTINEL);
54
println(
"
to signal the end of the list.
"
);
55
}
56
57
private
void
enterValue() {
58
int
val
=
readInt(
"
?
"
);
59
if
(val
==
SENTINEL) println(
"
No values were entrerd
"
);
60
if
(val
!=
SENTINEL) enterNextValue (val);
61
}
62
63
private
void
enterNextValue(
int
val) {
64
int
min
=
val;
65
int
max
=
val;
66
while
(
true
){
67
val
=
readInt(
"
?
"
);
68
if
(val
==
SENTINEL)
break
;
69
max
=
max(val,max);
70
min
=
min (val,min);
71
}
72
printResults(max, min);
73
}
74
75
private
void
printResults(
int
max,
int
min) {
76
println(
"
The Maximum is
"
+
max
+
"
.
"
);
77
println(
"
The Minimum is
"
+
min
+
"
.
"
);
78
79
}
80
81
private
int
max(
int
val,
int
max) {
82
if
(val
>
max)max
=
val;
83
return
max;
84
}
85
86
private
int
min(
int
val,
int
min) {
87
if
(val
<
min)min
=
val;
88
return
min;
89
}
90
}
Problem 6：Hailstones
这题名字挺怪：冰雹。基本没见过，说是牛人牛书里的不论给定一个数是奇或偶，最后总能折腾到1.（未证明）
1
/*
2
* File: Hailstone.java
3
* --------------------
4
* This program is a stub for the Hailstone problem, which computes
5
* Hailstone sequence described in Assignment #2.
6
*/
7
8
import
acm.program.
*
;
9
10
public
class
Hailstone
extends
ConsoleProgram {
11
12
public
void
run() {
13
int
n
=
readInt(
"
Enter a number:
"
);
14
int
i
=
0
;
15
while
( n
!=
1
) {
16
if
(n
%
2
==
0
){
17
println(n
+
"
is even, so I take half =
"
+
n
/
2
);
18
n
=
n
/
2
;
19
}
20
else
{
21
println(n
+
"
is odd, so I take 3n+1 =
"
+
(
3
*
n
+
1
));
22
n
=
3
*
n
+
1
;
23
}
24
i
++
;
25
}
26
println(
"
The porcess took
"
+
i
+
"
steps to reach 1.
"
);
27
}
28
29
}