Apply clang-format to Graham Scan in C++ (#641)

* Apply clang-format to Graham Scan in C++ * camel_case rather than pascalCase for C++ * Use const and references where possible * Replace print function with printing to ostream * Use const references in sorting lambda * Actually sort initial gift by polar angle

Author: berquist

contents/graham_scan/code/c++/graham_scan.cpp

@@ -1,65 +1,84 @@
+#include<algorithm>
+#include<cmath>
 #include<iostream>
 #include<vector>
-#include<algorithm>
 
-structpoint{
+structpoint{
 double x;
 double y;
 };
 
-boolccw(point a, point b, point c){
-return ((b.x - a.x)*(c.y - a.y) > (b.y - a.y)*(c.x - a.x));
+std::ostream& operator<<(std::ostream& os, const std::vector<point>& points){
+for (auto p : points){
+ os << "(" << p.x << ", " << p.y << ")\n";
+ }
+return os;
+}
+
+doubleccw(const point& a, const point& b, const point& c){
+return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
 }
 
-std::vector<point> grahamScan(std::vector<point> points){
-//selecting lowest point as pivot
-int lowIndex = 0;
-for(size_t i = 1; i < points.size(); i++){
-if(points[i].y < points[lowIndex].y){
- lowIndex = i;
+doublepolar_angle(const point& origin, const point& p){
+returnstd::atan2(p.y - origin.y, p.x - origin.x);
+}
+
+std::vector<point> graham_scan(std::vector<point>& points){
+// selecting lowest point as pivot
+size_t low_index = 0;
+for (size_t i = 1; i < points.size(); i++){
+if (points[i].y < points[low_index].y){
+ low_index = i;
  }
  }
-std::swap(points[0], points[lowIndex]);
+std::swap(points[0], points[low_index]);
  point pivot = points[0];
 
-//sorting points by polar angle
-std::sort(points.begin()+1, points.end(), [pivot](point a, point b){
-returnccw(pivot, a, b);
- });
+// sorting points by polar angle
+std::sort(
+ points.begin() + 1,
+ points.end(),
+ [&pivot](const point& pa, const point& pb){
+returnpolar_angle(pivot, pa) < polar_angle(pivot, pb);
+ });
 
-//creating convex hull
+//creating convex hull
 size_t m = 1;
-for(size_t i = 2; i < points.size(); i++){
-while(ccw(points[m - 1], points[m], points[i]) <= 0){
-if(m > 1){
-m--;
-continue;
-} elseif(i == points.size()){
-break;
-} else{
-i++;
-}
+for(size_t i = 2; i < points.size(); i++){
+while(ccw(points[m - 1], points[m], points[i]) <= 0){
+if(m > 1){
+ m--;
+continue;
+ } elseif(i == points.size()){
+break;
+ } else{
+ i++;
+ }
  }
  m++;
 std::swap(points[i], points[m]);
  }
 return std::vector<point>(points.begin(), points.begin() + m + 1);
 }
 
-voidprint(std::vector<point> points){
-for ( auto p : points){
- std::cout <<"(" << p.x << ", " << p.y <<")\n";
- }
-}
-
-intmain(){
- std::vector<point> points ={{-5, 2},{5, 7},{-6, -12},{-14, -14},{9, 9},
-{-1, -1},{-10, 11},{-6, 15},{-6, -8},{15, -9},
-{7, -7},{-2, -9},{6, -5},{0, 14},{2, 8}};
- std::cout << "original points are as follows:\n";
-print(points);
- std::vector<point> hull = grahamScan(points);
- std::cout << "points in hull are as follows:\n";
-print(hull);
+intmain(){
+ std::vector<point> points ={{-5, 2},
+{5, 7},
+{-6, -12},
+{-14, -14},
+{9, 9},
+{-1, -1},
+{-10, 11},
+{-6, 15},
+{-6, -8},
+{15, -9},
+{7, -7},
+{-2, -9},
+{6, -5},
+{0, 14},
+{2, 8}};
+ std::cout << "original points are as follows:\n" << points;
+const std::vector<point> hull = graham_scan(points);
+ std::cout << "points in hull are as follows:\n" << hull;
 return0;
 }

contents/graham_scan/graham_scan.md

@@ -27,7 +27,7 @@ We can find whether a rotation is counter-clockwise with trigonometric functions
 {% sample lang="java" %}
 [import:27-29, lang:"java"](code/java/GrahamScan.java)
 {% sample lang="cpp" %}
-[import:10-12, lang="cpp"](code/c++/graham_scan.cpp)
+[import:18-20, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 If the output of this function is 0, the points are collinear.
@@ -57,7 +57,7 @@ In the end, the code should look something like this:
 {% sample lang="java" %}
 [import:35-70, lang:"java"](code/java/GrahamScan.java)
 {% sample lang="cpp" %}
-[import:14-47, lang="cpp"](code/c++/graham_scan.cpp)
+[import:26-62, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 ### Bibliography