"Fundamentals of Algorithmic Design and analysis" 15, recent questions

1, because Java does not hold a single key-value pair of type is not very convenient to use

Package cn.xf.util;/** *  * function: Equivalent to a key value * @author Xiaofeng * @date June 18, 2017 * @fileName Genericpair.java * */PU Blic class Genericpair<e extends Object, F extends object> {private E first;private F second;public Genericpair () {} Public Genericpair (E first, F second) {This.first = First;this.second = Second;} @Overridepublic string toString () {string result = "[" + this.first.toString () + "," + this.second.toString () + "]"; return Result;} Public E GetFirst () {return first;} public void Setfirst (E first) {This.first = first;} Public F Getsecond () {return second;} public void Setsecond (F second) {this.second = second;}}

　　

Ask for a recent key-value pair problem

Package Cn.xf.algorithm.ch05;import Java.util.arraylist;import Java.util.list;import org.junit.test;import cn.xf.util.genericpair;/** * Features: Recent questions * @author Xiaofeng * @date June 18, 2017 * @fileName Minpath.java * */public class M Inpath {/** * * * @param the points array points stores n >= 2 points on the plane and sorts them in ascending order by the x-axis coordinates of those points seqxlist Seqylist * @param qpoints data qpoint The same point is stored with the points, except that it is sorted in ascending order of the y-axis coordinates of this point * output: Euclidean distance between nearest point pair */public double Efficientclosestpair (list<genericpair<        Double, double>> points, list<genericpair<double, double>> qpoints) {if (Points.size () <= 3) {    If less than 3 direct brute force comparison, the nearest distance to find a few points double countmin = double.max_value;    for (int i = 0; i < points.size (), ++i) {for (int j = 0; J < points.size (); ++j) {if (i = = j) {continue;    } Double temp = dist (Points.get (i), Points.get (j));    if (Temp < countmin) {countmin = temp;    }}} return countmin;    } else {int midindex = Points.size ()/2; Well, points, the front half pulls out POINTSL L.Ist<genericpair<double, double>> POINTSL = new arraylist<genericpair<double,double>> ();    for (int i = 0; i < Midindex; ++i) {Pointsl.add (Points.get (i)); }//Pull out the front half of the qpoints qpointsl//list<genericpair<double, double>> QPOINTSL = new Arraylist<genericpair <Double,Double>> ();//for (int i = 0; i < Midindex; ++i) {//Qpointsl.add (Qpoints.get (i));/}//PO INTSL's Y-sorted version as the new QPOINTSL list<genericpair<double, double>> QPOINTSL = new arraylist<genericpair<    Double,double>> ();    for (int i = 0; i < Midindex; ++i) {Qpointsl.add (Points.get (i));        } seqylist (QPOINTSL, 0, Qpointsl.size ()-1); Pull out the back half of the points. POINTSR list<genericpair<double, double>> pointsr = new arraylist<genericpair<    Double,double>> ();    for (int i = Midindex; I < points.size (); ++i) {Pointsr.add (Points.get (i)); }//Bar qpoints back half extracted qpointsr//list<genericpair<Double, double>> QPOINTSR = new arraylist<genericpair<double,double>> ();//for (int i = midindex; I &l T Qpoints.size (); ++i) {//Qpointsr.add (Qpoints.get (i)),//} list<genericpair<double, double>> QPOINTSR = new Array    List<genericpair<double,double>> ();    for (int i = Midindex; I < points.size (); ++i) {Qpointsr.add (Points.get (i));        } seqylist (QPOINTSR, 0, Qpointsr.size ()-1);    Enter recursive double dl = Efficientclosestpair (POINTSL, QPOINTSL) with the new collection point;        Double dr = Efficientclosestpair (POINTSR, QPOINTSR);    Two distances take small double dmin = minValue (DL, DR);    Double dmindist = Math.pow (DMin, 2);    Take X is worth the intermediate segment double midpointx = Points.get (Midindex). GetFirst (); All of these points x-midpointx the distance is smaller than the DMin list<genericpair<double, double>> pointsdmin = new arraylist<    Genericpair<double,double>> (); for (int i = 0; i < qpoints.size (); ++i) {//absolute value is smaller than the minimum distance if (Math.Abs (Qpoints.get (i). GETFirst ()-Midpointx) < DMin) {//the minimum distance from both sides, a smaller value, this is the data pointsdmin.add in ascending order of Y (Qpoints.get (i)); }}//Traverse all data in this collection, get the minimum distance for (int i = 0; i < pointsdmin.size (); ++i) {///if K is out of range, don't forget int k = i + 1    ;    if (k >= pointsdmin.size ()) {break;    }//squared difference Double minY2 = Math.pow (Pointsdmin.get (k). Getsecond ()-Pointsdmin.get (i). Getsecond (), 2); while (K < pointsdmin.size () && minY2 < dmindist) {//within the data range, then Y has a smaller squared difference than the smallest, then you can compare double tempmin = Math.pow (Pointsdmin.get (k). GetFirst ()-Pointsdmin.get (i). GetFirst (), 2) + Math.pow (Pointsdmin.get (k). Getsecond ()-    Pointsdmin.get (i). Getsecond (), 2);    Dmindist = MinValue (Tempmin, dmindist);    ++k;    }} return Math.sqrt (dmindist); }}public double MinValue (double DL, double dr) {if (DL < DR) {return DL;} else {return dr;}} public static Double Dist (genericpair<double, double> point1, genericpair<double, double> point2) {//Find out two points The distance between//squared difference Double DISTX = Math.Abs (Point1.getfirst ()-Point2.getfirst ());    Double disty = Math.Abs (Point1.getsecond ()-Point2.getsecond ()); The square root of the sum of the squared deviations is math.sqrt (DISTX * distx + disty * disty);} @Testpublic void Quiksorttest () {list<genericpair<double, double>> points = new Arraylist<genericpair <Double,Double>> (); List<genericpair<double, double>> qpoints = new arraylist<genericpair<double,double>> ();// 5,3,1,9,8,2,4,7,8//4,1,8,2,11,9,7,15,11genericpair<double, double> el1 = new genericpair<double, Double> (5d, 4d); Genericpair<double, double> el2 = new genericpair<double, double> (3d, 1d); Genericpair<double, double> el3 = new genericpair<double, double> (1d, 8d); Genericpair<double, double> el4 = new genericpair<double, Double> (9d, 2d); Genericpair<double, double> el5 = new genericpair<double, double> (8d, 11d); Genericpair<double, double> el6 = new genericpair<double, double> (2D, 9d); Genericpair<double, double> el7 = new genericpair<double, double> (4d, 7d); Genericpair<double, double> El8 = new genericpair<double, double> (7d, 15d);//genericpair<double, Double > el9 = new genericpair<double, double> (8d, 11d);p Oints.add (EL1);p oints.add (EL2);p oints.add (el3);p Oints.add (EL4);p oints.add (el5);p oints.add (el6);p oints.add (EL7);p oints.add (El8);//points.add (EL9); Qpoints.add (EL1); Qpoints.add (EL2); Qpoints.add (EL3); Qpoints.add (EL4); Qpoints.add (EL5); Qpoints.add (EL6); Qpoints.add (EL7); Qpoints.add (El8);//qpoints.add (EL9); Minpath MP = new Minpath () mp.seqxlist (points, 0, points.size ()-1); Mp.seqylist (qpoints, 0, Qpoints.size ()-1);//for (Gen Ericpair<double, double> temp:points) {//system.out.print (temp.tostring () + "\ t");//}double result = Mp.efficientclosestpair (points, qpoints); SYSTEM.OUT.PRINTLN (result);} /** * According to X Ascending * @param points * @return */public static void Seqxlist (List<genericpair<double, double>> points, int start, int end) {//Gets the middle point position and then divides it in half, traversing recursively if (start < end) {int mid = Hoarepartition (points, false, start, end); Seqxlist (points , start, mid-1); Seqxlist (points, Mid + 1, end);}} /** * in ascending order of Y * @param points * @return */public static void Seqylist (List<genericpair<double, double>> points, int start, int end) {//Gets the middle point position and then divides it in half, traversing recursively if (start < end) {int mid = Hoarepartition (points, true, start, end); seqyl IST (points, start, mid-1), Seqylist (points, Mid + 1, end);}} /** * Search for split points, and structured data, xory is used to determine whether the two sides are sorted by x-false or y-true sort * @param points * @return */public static int hoarepartition (list< Genericpair<double, Double>> points, Boolean xory, int start, int end) {if (start >= end) {return start;} Split Double temp = GetValue (Points.get (start), xory) on the first number of pairs, and//traverse until two stagger, or equal int leftindex = start + 1;int Rightindex = End;while (Leftindex < Rightindex) {//if traversing to the left is larger than the first, the right is smaller than the first number, exchanging data, in order to avoid unnecessary swapping while (GetValue ( Points.get (Leftindex), xory) < temp) {++leftindex;} while (GetvalUE (Points.get (Rightindex), xory) > Temp) {--rightindex;} If it is the last step, dislocation, and then swap, to avoid the extra swap swap (points, leftindex, rightindex);} From the last pair of misplaced data exchange back, but if this cycle has not been in, then there should be no swap swap (points, leftindex, rightindex);//Finally, the data place of J is switched to the data location starting as the intermediate point// If it is smaller than the middle value to be arranged, then do not change, change the sort if (GetValue (Points.get (start), xory) > GetValue (Points.get (Rightindex), xory)) swap (Points, start, rightindex); return rightindex;} Exchange data public static void Swap (list<genericpair<double, double>> points, int i, int j) {//Take out the I position data, I data is modified to J, Temp is data for I, Bar J is replaced with tempgenericpair tempi = Points.get (i); Genericpair TEMPJ = Points.get (j);p Oints.set (i, TEMPJ);p Oints.set (J, tempi);} /** * Xory is used to determine whether the two sides are sorted by x-false or y-true sort * @param pair * @param xory * @return */public static double GetValue (genericpair& Lt;double, double> pair, Boolean xory) {Double temp = 0;if (!xory) {///If True, then it is the first y//= Xtemp () to be judged Pair.getfirst);} E LSE {TEMP = Pair.getsecond ();} return temp;}}

　　

Nearest point distance

Questions, answers, online what " pigeon Nest Principle " is not very understand, to seek the interpretation of popular points ...

"Fundamentals of Algorithmic Design and analysis" 15, recent questions