三角形の周の長さが一番長くなるような線を３つ選ぶiPhoneアプリのサンプルコードを描いてみます。
#import “ViewController.h”
#include <memory>
#include <vector>
#include <algorithm>
using namespace std;
class EdgesSolver {
public:
float a, b, c;
void solveBestThree(vector<float>);
};
void EdgesSolver::solveBestThree(vector<float> edges) {
sort(edges.begin(), edges.end());
for (auto i = edges.size() – 3; i > 0; i++) {
if (edges[i+2] < edges[i+1] + edges[i]) {
a = edges[i]; // small
b = edges[i+1];
c = edges[i+2]; // max
return;
}
}
}
@interface ViewController ()
@end
@implementation ViewController
– (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor colorWithWhite:0.4 alpha:1];
[self createEdges];
}
– (void)createEdges {
for (int i=0; i<20; i++) {
CALayer *edge = [CALayer layer];
edge.name = @”edge”;
float l = (arc4random() % 2500) * 0.1 + 10;
edge.frame = CGRectMake(0, 0, l, 2);
edge.backgroundColor = [UIColor colorWithHue:i * 0.01 saturation:0.2 brightness:1 alpha:1].CGColor;
edge.position = CGPointMake(CGRectGetMidX(self.view.bounds), 7 * i + 100);
[self.view.layer addSublayer:edge];
}
}
– (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
vector<float> edges;
for (CALayer *l in self.view.layer.sublayers) {
edges.push_back(l.frame.size.width);
}
shared_ptr<EdgesSolver> cppClass(new EdgesSolver());
cppClass->solveBestThree(edges);
CALayer *maxL, *midL, *minL;
for (CALayer *l in self.view.layer.sublayers) {
if (l.frame.size.width == cppClass->a) {
minL = l;
} else if (l.frame.size.width == cppClass->b) {
midL = l;
} else if (l.frame.size.width == cppClass->c) {
l.position = CGPointMake(l.position.x, 240);
maxL = l;
}
}
float a = minL.frame.size.width;
float b = midL.frame.size.width;
float c = maxL.frame.size.width;
float cosB = (c*c + a*a – b*b) / (2.0 * a * c);
minL.position = CGPointMake(CGRectGetMaxX(maxL.frame) – a * cosB * 0.5, maxL.position.y – a * sqrt(1 – cosB*cosB) * 0.5);
minL.transform = CATransform3DMakeRotation(acos(cosB), 0, 0, 1);
float cosA = (c*c + b*b – a*a) / (2.0 * c * b);
midL.position = CGPointMake(maxL.frame.origin.x + b * cosA * 0.5, maxL.position.y – b * sqrt(1 – cosA*cosA) * 0.5);
midL.transform = CATransform3DMakeRotation(-acos(cosA), 0, 0, 1);
}
– (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
@end