-----------------------------------
MATLAB SCRIPT
-----------------------------------
x = random('unif',0,1,100,1);
y = random('unif',0,1,100,1);
k = convhull(x,y);
x1 = x(k);
y1 = y(k);
clf;
hold on;
plot(x,y,'b.');
plot(x1,y1,'r-');
----------------------------------
input:
8
2,3
10,7
6,9
8,13
3,10
5,12
3,12
12,11


output:
5
8,13
12,11
10,7
2,3
3,12
-----------------
input:
11
1,4
3,6
2,8
9,5
8,10
9,9
5,9
5,7
6,11
7,5
7,8

output:
6
6,11
8,10
9,9
9,5
1,4
2,8
----------------
input:
15
6,1
11,12
12,6
8,6
9,10
6,12
5,11
2,11
3,8
5,6
6,7
4,5
3,2
1,7
9,3

output:
8
6,12
11,12
12,6
9,3
6,1
3,2
1,7
2,11
-----------------
input:
15
-5,-10
0,-10
5,-5
-8,-5
0,-5
2,-2
1,1
5,0
-4,2.5
-5,9.5
1,7
5,5
6,8
10,5
-9.5,6

output:
8
-5,9.5
6,8
10,5
5,-5
0,-10
-5,-10
-8,-5
-9.5,6
------------------
input:
15
0.0769,0.7308
0.7209,0.6497
0.7649,0.6813
0.6579,0.0076
0.8104,0.6541
0.3742,0.9452
0.3062,0.6133
0.3707,0.7829
0.7067,0.0032
0.1684,0.7970
0.8137,0.6418
0.4662,0.1785
0.7223,0.5294
0.9949,0.2187
0.3625,0.5481

output:
9
0.4662,0.1785
0.6579,0.0076
0.7067,0.0032
0.9949,0.2187
0.8104,0.6541
0.3742,0.9452
0.1684,0.7970
0.0769,0.7308
0.4662,0.1785

-------------------
input 
15
0.5824,1.2880
5.8759,6.8683
4.1610,2.9724
1.8645,6.4722
0.6391,4.6376
0.7478,9.2279
3.1004,2.4172
9.4408,6.6016
9.8073,3.3229
5.5512,4.7675
9.8853,4.6877
6.9156,7.0593
2.4166,2.3995
8.0981,7.1720
9.3451,8.6520


output
7
0.6391,4.6376
0.5824,1.2880
9.8073,3.3229
9.8853,4.6877
9.3451,8.6520
0.7478,9.2279
0.6391,4.6376

---------------------
input:
20

0.4833,5.0677
4.6044,8.8413
7.9995,6.1557
2.8943,0.4639
6.9510,9.5192
2.5928,1.6903
7.1323,8.2667
7.2037,6.1138
7.3328,8.4730
6.2233,1.1412
9.8978,6.4922
1.5238,1.1482
2.0332,4.7341
8.1932,6.8318
0.5844,1.3330
5.3851,4.6408
1.9015,0.7125
5.9948,5.8122
2.9226,5.6598
0.9129,2.5526


output:

8
0.5844,1.3330
1.9015,0.7125
2.8943,0.4639
6.2233,1.1412
9.8978,6.4922
6.9510,9.5192
4.6044,8.8413
0.4833,5.0677