From 8875a083d2e2e36c20d4a208fbe1043629b93c9d Mon Sep 17 00:00:00 2001
From: Akash Dhiman <akash.d0407@gmail.com>
Date: Fri, 21 Jun 2019 05:29:55 +0530
Subject: [PATCH 1/5] implemented graham scan in cpp

---
 contents/graham_scan/code/c++/graham_scan.cpp | 102 ++++++++++++++++++
 contents/graham_scan/graham_scan.md           |   6 ++
 2 files changed, 108 insertions(+)
 create mode 100644 contents/graham_scan/code/c++/graham_scan.cpp

diff --git a/contents/graham_scan/code/c++/graham_scan.cpp b/contents/graham_scan/code/c++/graham_scan.cpp
new file mode 100644
index 000000000..fe06cf138
--- /dev/null
+++ b/contents/graham_scan/code/c++/graham_scan.cpp
@@ -0,0 +1,102 @@
+#include<iostream>
+#include<vector>
+
+struct point {
+  double x;
+  double y;
+};
+
+point origin;
+
+void swap(point &p1, point &p2){
+  point temp = p1;
+  p1 = p2;
+  p2 = temp;
+}
+
+int distSq(point p1, point p2){
+  return (p1.x - p2.x)*(p1.x - p2.x) +(p1.y - p2.y)*(p1.y - p2.y);
+}
+
+int ccwCheck(point a, point b, point c){
+
+  int crossProduct = (b.y - a.y) * (c.x - b.x) - (b.x - a.x) * (c.y - b.y);
+  if (crossProduct == 0)
+  {
+    return 0;
+  }
+  return ( crossProduct > 0)? -1 : 1;
+}
+
+int compare(const void *vp1, const void *vp2){
+
+   point *p1 = (point *)vp1;
+   point *p2 = (point *)vp2;
+
+   int o = ccwCheck(origin, *p1, *p2);
+   if (o == 0)
+     return (distSq(origin, *p2) >= distSq(origin, *p1))? -1 : 1;
+
+   return (o == 1)? -1: 1;
+}
+
+void print(std::vector<point> points)
+{
+  std::cout << "the points of hull are as follows:\n";
+  for (size_t i = 0; i < points.size(); i++) {
+    std::cout << "(" << points[i].x << "," << points[i].y << ")\n";
+  }
+}
+
+std::vector<point> grahamScan(std::vector<point> points){
+  //selecting origin(the element with y minimum)
+  double yMin = points[0].y;
+  int min = 0;
+  for (size_t i = 1; i < points.size(); i++) {
+    double y = points[i].y;
+    if ((y < yMin) || (yMin == y && points[i].x < points[min].x)){
+      yMin = points[i].y;
+      min = i;
+    }
+  }
+  swap(points[0], points[min]);
+  origin = points[0];
+
+  //sorting by polar angle and removing duplicates
+  qsort(&points[1], points.size() - 1, sizeof(point), compare);
+  std::vector<point> pointsSorted;
+  pointsSorted.push_back(origin);
+  for(size_t i = 1; i < points.size(); i++){
+    while(i < points.size() - 1 && ccwCheck(origin, points[i],
+      points[i+1]) == 0){
+      i++;
+    }
+    pointsSorted.push_back(points[i]);
+  }
+
+  //creating the convex hull
+  std::vector<point> hull;
+  hull.push_back(points[0]);
+  hull.push_back(points[1]);
+  hull.push_back(points[2]);
+  for (size_t i = 3; i <= pointsSorted.size(); i++) {
+    while (ccwCheck(hull.at(hull.size()-2), hull.at(hull.size()-1),
+    pointsSorted[i]) != 1)
+      {
+        hull.pop_back();
+      }
+      hull.push_back(points[i]);
+  }
+  return hull;
+}
+
+int main()
+{
+  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::vector<point> hull = grahamScan(points);
+  print(hull);
+  return 0;
+}
diff --git a/contents/graham_scan/graham_scan.md b/contents/graham_scan/graham_scan.md
index 66dec5f60..fc799004b 100644
--- a/contents/graham_scan/graham_scan.md
+++ b/contents/graham_scan/graham_scan.md
@@ -26,6 +26,8 @@ We can find whether a rotation is counter-clockwise with trigonometric functions
 [import:13-15, lang:"go"](code/golang/graham.go)
 {% sample lang="java" %}
 [import:27-29, lang:"java"](code/java/GrahamScan.java)
+{% sample lang="cpp" %}
+[import:21-29, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 If the output of this function is 0, the points are collinear.
@@ -54,6 +56,8 @@ In the end, the code should look something like this:
 [import:21-42, lang:"go"](code/golang/graham.go)
 {% sample lang="java" %}
 [import:35-70, lang:"java"](code/java/GrahamScan.java)
+{% sample lang="cpp" %}
+[import:51-91, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 ### Bibliography
@@ -77,6 +81,8 @@ In the end, the code should look something like this:
 [import, lang:"go"](code/golang/graham.go)
 {% sample lang="java" %}
 [import, lang:"java"](code/java/GrahamScan.java)
+{% sample lang="cpp" %}
+[import, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 <script>

From 248e5aeff5392d16415ecf288f61c1ad5f73f506 Mon Sep 17 00:00:00 2001
From: Akash Dhiman <akash.d0407@gmail.com>
Date: Sun, 7 Jul 2019 01:22:17 +0530
Subject: [PATCH 2/5] improved code for graham-scan implementation in cpp

---
 CONTRIBUTORS.md                               |   2 +
 contents/graham_scan/code/c++/graham_scan.cpp | 120 ++++++------------
 contents/graham_scan/graham_scan.md           |   4 +-
 3 files changed, 46 insertions(+), 80 deletions(-)

diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 8029ab0f1..e6f1fc2f1 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -44,3 +44,5 @@ This file lists everyone, who contributed to this repo and wanted to show up her
 - Björn Heinrichs 
 - Olav Sundfør
 - dovisutu
+- Antetokounpo
+- Akash Dhiman
diff --git a/contents/graham_scan/code/c++/graham_scan.cpp b/contents/graham_scan/code/c++/graham_scan.cpp
index fe06cf138..8d74386e8 100644
--- a/contents/graham_scan/code/c++/graham_scan.cpp
+++ b/contents/graham_scan/code/c++/graham_scan.cpp
@@ -1,101 +1,65 @@
 #include<iostream>
 #include<vector>
+#include<algorithm>
 
-struct point {
-  double x;
-  double y;
+struct point{
+  float x;
+  float y;
 };
 
-point origin;
-
-void swap(point &p1, point &p2){
-  point temp = p1;
-  p1 = p2;
-  p2 = temp;
-}
-
-int distSq(point p1, point p2){
-  return (p1.x - p2.x)*(p1.x - p2.x) +(p1.y - p2.y)*(p1.y - p2.y);
-}
-
-int ccwCheck(point a, point b, point c){
-
-  int crossProduct = (b.y - a.y) * (c.x - b.x) - (b.x - a.x) * (c.y - b.y);
-  if (crossProduct == 0)
-  {
-    return 0;
-  }
-  return ( crossProduct > 0)? -1 : 1;
-}
-
-int compare(const void *vp1, const void *vp2){
-
-   point *p1 = (point *)vp1;
-   point *p2 = (point *)vp2;
-
-   int o = ccwCheck(origin, *p1, *p2);
-   if (o == 0)
-     return (distSq(origin, *p2) >= distSq(origin, *p1))? -1 : 1;
-
-   return (o == 1)? -1: 1;
-}
-
-void print(std::vector<point> points)
-{
-  std::cout << "the points of hull are as follows:\n";
-  for (size_t i = 0; i < points.size(); i++) {
-    std::cout << "(" << points[i].x << "," << points[i].y << ")\n";
-  }
+bool ccw(point a, point b, 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 origin(the element with y minimum)
-  double yMin = points[0].y;
-  int min = 0;
+  //selecting lowest point as pivot
+  int lowIndex = 0;
   for (size_t i = 1; i < points.size(); i++) {
-    double y = points[i].y;
-    if ((y < yMin) || (yMin == y && points[i].x < points[min].x)){
-      yMin = points[i].y;
-      min = i;
+    if(points[i].y < points[lowIndex].y){
+      lowIndex = i;
     }
   }
-  swap(points[0], points[min]);
-  origin = points[0];
-
-  //sorting by polar angle and removing duplicates
-  qsort(&points[1], points.size() - 1, sizeof(point), compare);
-  std::vector<point> pointsSorted;
-  pointsSorted.push_back(origin);
-  for(size_t i = 1; i < points.size(); i++){
-    while(i < points.size() - 1 && ccwCheck(origin, points[i],
-      points[i+1]) == 0){
-      i++;
+  std::swap<point>(points[0], points[lowIndex]);
+  point pivot = points[0];
+
+  //sorting points by polar angle
+  sort(points.begin()+1, points.end(), [pivot](point a, point b){
+    return ccw(pivot, a, b);
+  });
+
+  //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;
+            } else if (i == points.size()) {
+                break;
+            } else {
+                i++;
+            }
     }
-    pointsSorted.push_back(points[i]);
+    m++;
+    std::swap<point>(points[i],points[m]);
   }
+  std::vector<point>::const_iterator first = points.begin();
+  std::vector<point>::const_iterator last = points.begin()+m;
+  std::vector<point> hull(first, last);
+  return hull;
+}
 
-  //creating the convex hull
-  std::vector<point> hull;
-  hull.push_back(points[0]);
-  hull.push_back(points[1]);
-  hull.push_back(points[2]);
-  for (size_t i = 3; i <= pointsSorted.size(); i++) {
-    while (ccwCheck(hull.at(hull.size()-2), hull.at(hull.size()-1),
-    pointsSorted[i]) != 1)
-      {
-        hull.pop_back();
-      }
-      hull.push_back(points[i]);
+void print(std::vector<point> points){
+  std::cout << "points in hull are as follows: \n";
+  for (size_t i = 0; i < points.size(); i++) {
+    std::cout <<"(" << points[i].x << ", "<< points[i].y <<")\n";
   }
-  return hull;
 }
 
-int main()
-{
+int main(){
   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::vector<point> hull = grahamScan(points);
   print(hull);
   return 0;
diff --git a/contents/graham_scan/graham_scan.md b/contents/graham_scan/graham_scan.md
index fc799004b..ad4a2d03e 100644
--- a/contents/graham_scan/graham_scan.md
+++ b/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:21-29, lang="cpp"](code/c++/graham_scan.cpp)
+[import:10-12, 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:51-91, lang="cpp"](code/c++/graham_scan.cpp)
+[import:14-50, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 ### Bibliography

From f3e18a9efb162d9f275438f176b728fbf0563cc1 Mon Sep 17 00:00:00 2001
From: Akash Dhiman <akash.d0407@gmail.com>
Date: Sun, 7 Jul 2019 22:48:02 +0530
Subject: [PATCH 3/5] improved implementation based on suggestions

---
 contents/graham_scan/code/c++/graham_scan.cpp | 37 +++++++++----------
 contents/graham_scan/graham_scan.md           |  2 +-
 2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/contents/graham_scan/code/c++/graham_scan.cpp b/contents/graham_scan/code/c++/graham_scan.cpp
index 8d74386e8..3e4e34190 100644
--- a/contents/graham_scan/code/c++/graham_scan.cpp
+++ b/contents/graham_scan/code/c++/graham_scan.cpp
@@ -1,10 +1,10 @@
-#include<iostream>
-#include<vector>
-#include<algorithm>
+#include <iostream>
+#include <vector>
+#include <algorithm>
 
 struct point{
-  float x;
-  float y;
+  double x;
+  double y;
 };
 
 bool ccw(point a, point b, point c){
@@ -14,45 +14,41 @@ bool ccw(point a, point b, point c){
 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++) {
+  for(size_t i = 1; i < points.size(); i++) {
     if(points[i].y < points[lowIndex].y){
       lowIndex = i;
     }
   }
-  std::swap<point>(points[0], points[lowIndex]);
+  std::swap(points[0], points[lowIndex]);
   point pivot = points[0];
 
   //sorting points by polar angle
-  sort(points.begin()+1, points.end(), [pivot](point a, point b){
+  std::sort(points.begin()+1, points.end(), [pivot](point a, point b){
     return ccw(pivot, a, b);
   });
 
   //creating convex hull
   size_t m = 1;
-  for (size_t i = 2; i <= points.size(); i++) {
+  for(size_t i = 2; i <= points.size(); i++) {
     while(ccw(points[m - 1], points[m], points[i]) <= 0){
-      if (m > 1) {
+      if(m > 1) {
                 m--;
                 continue;
-            } else if (i == points.size()) {
+            } else if(i == points.size()) {
                 break;
             } else {
                 i++;
             }
     }
     m++;
-    std::swap<point>(points[i],points[m]);
+    std::swap(points[i], points[m]);
   }
-  std::vector<point>::const_iterator first = points.begin();
-  std::vector<point>::const_iterator last = points.begin()+m;
-  std::vector<point> hull(first, last);
-  return hull;
+  return std::vector<point>(points.begin(), points.begin() + m);
 }
 
 void print(std::vector<point> points){
-  std::cout << "points in hull are as follows: \n";
-  for (size_t i = 0; i < points.size(); i++) {
-    std::cout <<"(" << points[i].x << ", "<< points[i].y <<")\n";
+  for ( auto p : points){
+    std::cout <<"(" << p.x << ", " << p.y <<")\n";
   }
 }
 
@@ -60,7 +56,10 @@ int main(){
   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);
   return 0;
 }
diff --git a/contents/graham_scan/graham_scan.md b/contents/graham_scan/graham_scan.md
index ad4a2d03e..e0323d961 100644
--- a/contents/graham_scan/graham_scan.md
+++ b/contents/graham_scan/graham_scan.md
@@ -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:14-50, lang="cpp"](code/c++/graham_scan.cpp)
+[import:14-47, lang="cpp"](code/c++/graham_scan.cpp)
 {% endmethod %}
 
 ### Bibliography

From bedad3e194fc52f68cd859be0135fd4c53119284 Mon Sep 17 00:00:00 2001
From: Akash Dhiman <akash.d0407@gmail.com>
Date: Sun, 7 Jul 2019 23:56:43 +0530
Subject: [PATCH 4/5] fixed the runtimeerror

---
 contents/graham_scan/code/c++/graham_scan.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/contents/graham_scan/code/c++/graham_scan.cpp b/contents/graham_scan/code/c++/graham_scan.cpp
index 3e4e34190..8b3d8f0cd 100644
--- a/contents/graham_scan/code/c++/graham_scan.cpp
+++ b/contents/graham_scan/code/c++/graham_scan.cpp
@@ -29,7 +29,7 @@ std::vector<point> grahamScan(std::vector<point> points){
 
   //creating convex hull
   size_t m = 1;
-  for(size_t i = 2; i <= points.size(); i++) {
+  for(size_t i = 2; i < points.size(); i++) {
     while(ccw(points[m - 1], points[m], points[i]) <= 0){
       if(m > 1) {
                 m--;
@@ -43,7 +43,7 @@ std::vector<point> grahamScan(std::vector<point> points){
     m++;
     std::swap(points[i], points[m]);
   }
-  return std::vector<point>(points.begin(), points.begin() + m);
+  return std::vector<point>(points.begin(), points.begin() + m + 1);
 }
 
 void print(std::vector<point> points){

From c4e859dd7611ed86ea2847f30191cb800de6bd0e Mon Sep 17 00:00:00 2001
From: Akash Dhiman <akash.d0407@gmail.com>
Date: Mon, 8 Jul 2019 13:39:58 +0530
Subject: [PATCH 5/5] fixed runtime error based on suggestion

---
 contents/graham_scan/code/c++/graham_scan.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contents/graham_scan/code/c++/graham_scan.cpp b/contents/graham_scan/code/c++/graham_scan.cpp
index 8b3d8f0cd..1e24b1bfe 100644
--- a/contents/graham_scan/code/c++/graham_scan.cpp
+++ b/contents/graham_scan/code/c++/graham_scan.cpp
@@ -8,7 +8,7 @@ struct point{
 };
 
 bool ccw(point a, point b, point c){
-  return ((b.x - a.x)*(c.y - a.y) >= (b.y - a.y)*(c.x - a.x));
+  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){