logo

Optimal placering av punkten för att minimera det totala avståndet

Prova det på GfG Practice Optimal placering av punkten för att minimera det totala avståndet' title= #practiceLinkDiv { display: ingen !viktigt; }

Givet en uppsättning punkter som och en linje som ax+by+c = 0. Vi måste hitta en punkt på en given linje för vilken summan av avstånden från en given uppsättning punkter är minimum. 

Exempel:  



använder internet
In above figure optimum location of point of x - y - 3 = 0 line is (2 -1) whose total distance with other points is 20.77 which is minimum obtainable total distance.
Recommended Practice Optimal placering av punkten för att minimera det totala avståndet Prova!

Om vi ​​tar en punkt på en given linje på oändligt avstånd så kommer den totala avståndskostnaden att vara oändlig nu när vi flyttar denna punkt på linjen mot givna punkter börjar den totala avståndskostnaden att minska och efter en tid börjar den återigen öka vilket nådde oändligt på den andra oändliga änden av linjen så avståndskostnadskurvan ser ut som en U-kurva och vi måste hitta bottenvärdet för denna U-kurva. 

Eftersom U-kurvan inte ökar eller minskar monotont kan vi inte använda binär sökning för att hitta botten mest punkt här kommer vi att använda ternär sökning för att hitta botten mest punkt ternär sökning hoppar över en tredjedel av sökutrymmet vid varje iteration du kan läsa mer om ternär sökning här

Så lösningen fortsätter enligt följande vi börjar med låg och hög initierad som några minsta respektive största värden, sedan startar vi iteration i varje iteration vi beräknar två mids mid1 och mid2 som representerar 1/3:e och 2/3:e position i sökutrymme vi beräknar det totala avståndet för alla punkter med mid1 och mid2 och uppdaterar lågt eller högt genom att jämföra dessa avstånd tills de är ungefär lika höga tills det är högt. 

cm till fot och tum
C++
// C/C++ program to find optimum location and total cost #include    using namespace std; #define sq(x) ((x) * (x)) #define EPS 1e-6 #define N 5 // structure defining a point struct point {  int x y;  point() {}  point(int x int y)  : x(x)   y(y)  {  } }; // structure defining a line of ax + by + c = 0 form struct line {  int a b c;  line(int a int b int c)  : a(a)   b(b)   c(c)  {  } }; // method to get distance of point (x y) from point p double dist(double x double y point p) {  return sqrt(sq(x - p.x) + sq(y - p.y)); } /* Utility method to compute total distance all points  when choose point on given line has x-coordinate  value as X */ double compute(point p[] int n line l double X) {  double res = 0;  // calculating Y of chosen point by line equation  double Y = -1 * (l.c + l.a * X) / l.b;  for (int i = 0; i < n; i++)  res += dist(X Y p[i]);  return res; } // Utility method to find minimum total distance double findOptimumCostUtil(point p[] int n line l) {  double low = -1e6;  double high = 1e6;  // loop until difference between low and high  // become less than EPS  while ((high - low) > EPS) {  // mid1 and mid2 are representative x co-ordiantes  // of search space  double mid1 = low + (high - low) / 3;  double mid2 = high - (high - low) / 3;  //  double dist1 = compute(p n l mid1);  double dist2 = compute(p n l mid2);  // if mid2 point gives more total distance  // skip third part  if (dist1 < dist2)  high = mid2;  // if mid1 point gives more total distance  // skip first part  else  low = mid1;  }  // compute optimum distance cost by sending average  // of low and high as X  return compute(p n l (low + high) / 2); } // method to find optimum cost double findOptimumCost(int points[N][2] line l) {  point p[N];  // converting 2D array input to point array  for (int i = 0; i < N; i++)  p[i] = point(points[i][0] points[i][1]);  return findOptimumCostUtil(p N l); } // Driver code to test above method int main() {  line l(1 -1 -3);  int points[N][2] = {  { -3 -2 } { -1 0 } { -1 2 } { 1 2 } { 3 4 }  };  cout << findOptimumCost(points l) << endl;  return 0; } 
Java
// A Java program to find optimum location // and total cost class GFG {  static double sq(double x) { return ((x) * (x)); }  static int EPS = (int)(1e-6) + 1;  static int N = 5;  // structure defining a point  static class point {  int x y;  point() {}  public point(int x int y)  {  this.x = x;  this.y = y;  }  };  // structure defining a line of ax + by + c = 0 form  static class line {  int a b c;  public line(int a int b int c)  {  this.a = a;  this.b = b;  this.c = c;  }  };  // method to get distance of point (x y) from point p  static double dist(double x double y point p)  {  return Math.sqrt(sq(x - p.x) + sq(y - p.y));  }  /* Utility method to compute total distance all points  when choose point on given line has x-coordinate  value as X */  static double compute(point p[] int n line l  double X)  {  double res = 0;  // calculating Y of chosen point by line equation  double Y = -1 * (l.c + l.a * X) / l.b;  for (int i = 0; i < n; i++)  res += dist(X Y p[i]);  return res;  }  // Utility method to find minimum total distance  static double findOptimumCostUtil(point p[] int n  line l)  {  double low = -1e6;  double high = 1e6;  // loop until difference between low and high  // become less than EPS  while ((high - low) > EPS) {  // mid1 and mid2 are representative x  // co-ordiantes of search space  double mid1 = low + (high - low) / 3;  double mid2 = high - (high - low) / 3;  double dist1 = compute(p n l mid1);  double dist2 = compute(p n l mid2);  // if mid2 point gives more total distance  // skip third part  if (dist1 < dist2)  high = mid2;  // if mid1 point gives more total distance  // skip first part  else  low = mid1;  }  // compute optimum distance cost by sending average  // of low and high as X  return compute(p n l (low + high) / 2);  }  // method to find optimum cost  static double findOptimumCost(int points[][] line l)  {  point[] p = new point[N];  // converting 2D array input to point array  for (int i = 0; i < N; i++)  p[i] = new point(points[i][0] points[i][1]);  return findOptimumCostUtil(p N l);  }  // Driver Code  public static void main(String[] args)  {  line l = new line(1 -1 -3);  int points[][] = { { -3 -2 }  { -1 0 }  { -1 2 }  { 1 2 }  { 3 4 } };  System.out.println(findOptimumCost(points l));  } } // This code is contributed by Rajput-Ji 
Python3
# A Python3 program to find optimum location # and total cost import math class Optimum_distance: # Class defining a point class Point: def __init__(self x y): self.x = x self.y = y # Class defining a line of ax + by + c = 0 form class Line: def __init__(self a b c): self.a = a self.b = b self.c = c # Method to get distance of point  # (x y) from point p def dist(self x y p): return math.sqrt((x - p.x) ** 2 + (y - p.y) ** 2) # Utility method to compute total distance # all points when choose point on given # line has x-coordinate value as X def compute(self p n l x): res = 0 y = -1 * (l.a*x + l.c) / l.b # Calculating Y of chosen point # by line equation for i in range(n): res += self.dist(x y p[i]) return res # Utility method to find minimum total distance def find_Optimum_cost_untill(self p n l): low = -1e6 high = 1e6 eps = 1e-6 + 1 # Loop until difference between low # and high become less than EPS while((high - low) > eps): # mid1 and mid2 are representative x # co-ordiantes of search space mid1 = low + (high - low) / 3 mid2 = high - (high - low) / 3 dist1 = self.compute(p n l mid1) dist2 = self.compute(p n l mid2) # If mid2 point gives more total  # distance skip third part if (dist1 < dist2): high = mid2 # If mid1 point gives more total # distance skip first part else: low = mid1 # Compute optimum distance cost by  # sending average of low and high as X return self.compute(p n l (low + high) / 2) # Method to find optimum cost def find_Optimum_cost(self p l): n = len(p) p_arr = [None] * n # Converting 2D array input to point array for i in range(n): p_obj = self.Point(p[i][0] p[i][1]) p_arr[i] = p_obj return self.find_Optimum_cost_untill(p_arr n l) # Driver Code if __name__ == '__main__': obj = Optimum_distance() l = obj.Line(1 -1 -3) p = [ [ -3 -2 ] [ -1 0 ] [ -1 2 ] [ 1 2 ] [ 3 4 ] ] print(obj.find_Optimum_cost(p l)) # This code is contributed by Sulu_mufi 
C#
// C# program to find optimum location // and total cost using System; class GFG {  static double sq(double x) { return ((x) * (x)); }  static int EPS = (int)(1e-6) + 1;  static int N = 5;  // structure defining a point  public class point {  public int x y;  public point() {}  public point(int x int y)  {  this.x = x;  this.y = y;  }  };  // structure defining a line  // of ax + by + c = 0 form  public class line {  public int a b c;  public line(int a int b int c)  {  this.a = a;  this.b = b;  this.c = c;  }  };  // method to get distance of  // point (x y) from point p  static double dist(double x double y point p)  {  return Math.Sqrt(sq(x - p.x) + sq(y - p.y));  }  /* Utility method to compute total distance  of all points when choose point on  given line has x-coordinate value as X */  static double compute(point[] p int n line l  double X)  {  double res = 0;  // calculating Y of chosen point  // by line equation  double Y = -1 * (l.c + l.a * X) / l.b;  for (int i = 0; i < n; i++)  res += dist(X Y p[i]);  return res;  }  // Utility method to find minimum total distance  static double findOptimumCostUtil(point[] p int n  line l)  {  double low = -1e6;  double high = 1e6;  // loop until difference between  // low and high become less than EPS  while ((high - low) > EPS) {  // mid1 and mid2 are representative  // x co-ordiantes of search space  double mid1 = low + (high - low) / 3;  double mid2 = high - (high - low) / 3;  double dist1 = compute(p n l mid1);  double dist2 = compute(p n l mid2);  // if mid2 point gives more total distance  // skip third part  if (dist1 < dist2)  high = mid2;  // if mid1 point gives more total distance  // skip first part  else  low = mid1;  }  // compute optimum distance cost by  // sending average of low and high as X  return compute(p n l (low + high) / 2);  }  // method to find optimum cost  static double findOptimumCost(int[ ] points line l)  {  point[] p = new point[N];  // converting 2D array input to point array  for (int i = 0; i < N; i++)  p[i] = new point(points[i 0] points[i 1]);  return findOptimumCostUtil(p N l);  }  // Driver Code  public static void Main(String[] args)  {  line l = new line(1 -1 -3);  int[ ] points = { { -3 -2 }  { -1 0 }  { -1 2 }  { 1 2 }  { 3 4 } };  Console.WriteLine(findOptimumCost(points l));  } } // This code is contributed by 29AjayKumar 
JavaScript
<script> // A JavaScript program to find optimum location // and total cost function sq(x) {  return x*x; } let EPS = (1e-6) + 1; let N = 5; // structure defining a point class point {  constructor(xy)  {  this.x=x;  this.y=y;  } } // structure defining a line of ax + by + c = 0 form class line {  constructor(abc)  {  this.a = a;  this.b = b;  this.c = c;  }   } // method to get distance of point (x y) from point p function dist(xyp) {  return Math.sqrt(sq(x - p.x) + sq(y - p.y)); } /* Utility method to compute total distance all points  when choose point on given line has x-coordinate  value as X */ function compute(pnlX) {  let res = 0;    // calculating Y of chosen point by line equation  let Y = -1 * (l.c + l.a * X) / l.b;  for (let i = 0; i < n; i++)  res += dist(X Y p[i]);    return res; } // Utility method to find minimum total distance function findOptimumCostUtil(pnl) {  let low = -1e6;  let high = 1e6;    // loop until difference between low and high  // become less than EPS  while ((high - low) > EPS) {  // mid1 and mid2 are representative x  // co-ordiantes of search space  let mid1 = low + (high - low) / 3;  let mid2 = high - (high - low) / 3;    let dist1 = compute(p n l mid1);  let dist2 = compute(p n l mid2);    // if mid2 point gives more total distance  // skip third part  if (dist1 < dist2)  high = mid2;    // if mid1 point gives more total distance  // skip first part  else  low = mid1;  }    // compute optimum distance cost by sending average  // of low and high as X  return compute(p n l (low + high) / 2); } // method to find optimum cost function findOptimumCost(pointsl) {  let p = new Array(N);    // converting 2D array input to point array  for (let i = 0; i < N; i++)  p[i] = new point(points[i][0] points[i][1]);    return findOptimumCostUtil(p N l); } // Driver Code let l = new line(1 -1 -3); let points= [[ -3 -2 ]  [ -1 0 ]  [ -1 2 ]  [ 1 2 ]  [ 3 4 ]]; document.write(findOptimumCost(points l)); // This code is contributed by rag2127 </script> 

Produktion
20.7652

Tidskomplexitet:2
Hjälputrymme: På)