我想从我的数据集中找到最接近的值。第一个值返回正确的数据，而第二个值返回最后的最近数据。例如，如果我有7, 11, 12, 15, 17, 20并且我的参数值是10，那么它应该返回第一个最近值= 11和第二个最近值=12。但是当我尝试时，第二个值不是12而是20。第一个值将为向右返回，但第二个最近的值将始终显示最后一个最近的值，而不是第二个最近的值。
这是我的代码：
String closestPosition = null;
ArrayList<Router> wifis = db.getFriendlyWifis(building);
double min_distance = positionData.uDistance(positionsData.get(0), wifis);
closestPosition = positionsData.get(0).getName();
String res = "";
res += closestPosition + "\n" + min_distance;
res += "\n" + positionsData.get(0).toString();
int j=0;
for (int i = 1; i < positionsData.size(); i++) {
double distance = positionData.uDistance(positionsData.get(i), wifis);
res += "\n" + positionsData.get(i).getName() + "\n" + distance;
res += "\n" + positionsData.get(i).toString();
if (distance < min_distance) {
min_distance = distance;
closestPosition = positionsData.get(i).getName();
j=i;
}
}
if (min_distance == PositionData.MAX_DISTANCE){
closestPosition="OUT OF RANGE";
Toast.makeText(this,"You are out of range of the selected building",Toast.LENGTH_LONG).show();
}
result.setText("Nearest point : "+ closestPosition);
res += "\nCurrent:\n" + positionData.toString();
Log.v("Result",res);
//////////////////////////////////////////////////
min_distance = positionData.uDistance(positionsData.get(0), wifis);
String closestPosition2 = null;
closestPosition2 = positionsData.get(0).getName();
res = "";
res += closestPosition2 + "\n" + min_distance;
res += "\n" + positionsData.get(0).toString();
for (int i = 1; i < positionsData.size(); i=i+2) { if(j!=i){
double distance = positionData.uDistance(positionsData.get(i), wifis);
res += "\n" + positionsData.get(i).getName() + "\n" + distance;
res += "\n" + positionsData.get(i).toString();
closestPosition2 = positionsData.get(i).getName();//////////////////////////
if(closestPosition2.equals(closestPosition))
continue;
if (distance < min_distance) {
min_distance = distance;
closestPosition2 = positionsData.get(i).getName();
}
}
}
if (min_distance == PositionData.MAX_DISTANCE){
closestPosition2="OUT OF RANGE";
Toast.makeText(this,"You are out of range of the selected building",Toast.LENGTH_LONG).show();
}
result2.setText("Nearest point : "+ closestPosition2);
以下是输出：
V/closest1:: f
V/closest2:: e
这是日志：
d
36.0
d(4.0,4.0)
UGM-Secure : -63.0
eduroam : -63.0
UGM-Hotspot : -42.0
a
64.0
a(1.0,1.0)
UGM-Hotspot : -40.0
f
17.0
f(6.0,6.0)
UGM-Secure : -65.0
eduroam : -66.0
UGM-Hotspot : -46.0
b
25.0
b(2.0,2.0)
UGM-Secure : -60.0
eduroam : -59.0
UGM-Hotspot : -48.0
c
89.0
c(3.0,3.0)
UGM-Secure : -60.0
eduroam : -59.0
UGM-Hotspot : -40.0
e
94.0
e(5.0,5.0)
UGM-Secure : -65.0
eduroam : -66.0
UGM-Hotspot : -39.0
如果第一个最近的值是f且值为17，则第二个最近的值是b还是d对吗？但是为什么它返回具有最大价值的e？我实际上也在寻找第3个最接近的值，如果还有其他方法可以找到第3个最接近的值，那将会很棒。
编辑：这是我的PositionData类
public class PositionData implements Serializable {
public static final int MAX_DISTANCE=99999999;
private String name;
double x;
double y;
public static final int MINIMUM_COMMON_ROUTERS=1;
public HashMap<String, Double> values;
public HashMap<String,String> routers;
public PositionData(String name, double x, double y) {
// TODO Auto-generated constructor stub
this.name=name;
this.x=x;
this.y=y;
values = new HashMap<String, Double>();
routers = new HashMap<String, String>();
}
public void addValue(Router router, double strength){
values.put(router.getBSSID(), strength);
routers.put(router.getBSSID(),router.getSSID());
}
public String getName() {
return name;
}
public Double getX() {
return x;
}
public Double getY() {
return y;
}
public String toString() {
String result="";
result+=name+"("+x+","+y+")"+"\n";
for(Map.Entry<String, Double> e: this.values.entrySet())
result+=routers.get(e.getKey())+" : "+e.getValue().toString()+"\n";
return result;
}
public HashMap<String, Double> getValues() {
return values;
}
public double uDistance(PositionData arg,ArrayList<Router> friendlyWifis){
double sum=0;
double count=0;
for(Map.Entry<String, Double> e: this.values.entrySet()){
Double v;
//Log.v("Key : ",arg.values.get(e.getKey()).toString());
if(isFriendlyWifi(friendlyWifis,e.getKey()) && arg.values.containsKey(e.getKey()))
{
v=arg.values.get(e.getKey());
sum+=Math.pow((v-e.getValue()),2);
count++;
}
}
if(count<MINIMUM_COMMON_ROUTERS){
sum=MAX_DISTANCE;
}
return sum;
}
private boolean isFriendlyWifi(ArrayList<Router> wifis, String bssid){
for(int i=0;i<wifis.size();i++){
if(wifis.get(i).getBSSID().equals(bssid))
return true;
}
return false;
}
}
答案 0 :(得分：0)
这将为您提供最接近的值
int[] numbers = new int[10];
numbers[0] = 100;
numbers[1] = -34200;
numbers[2] = 3040;
numbers[3] = 400433;
numbers[4] = 500;
numbers[5] = -100;
numbers[6] = -200;
numbers[7] = 532;
numbers[8] = 6584;
numbers[9] = -945;
int myNumber = 50;
int distance = Math.abs(numbers[0] - myNumber);
int idx = 0;
for(int c = 1; c < numbers.length; c++){
int cdistance = Math.abs(numbers[c] - myNumber);
if(cdistance < distance){
idx = c;
distance = cdistance;
}
}
int nearestNumber = numbers[idx];
答案 1 :(得分：0)
尝试以下代码：
private final static int POSITIONS_ARRAY_SIZE = 3; //Global constant in the Activity.
String closestPosition = null;
String closestPosition2 = null;
String closestPosition3 = null;
ArrayList<Router> wifis = db.getFriendlyWifis(building);
boolean flagPositionInserted;
ArrayList<Integer> min_distance_positions = new ArrayList<>();
//Get the first value (position = 0).
double min_distance = positionData.uDistance(positionsData.get(0), wifis);
min_distance_positions.add(0);
String res = "";
res += closestPosition + "\n" + min_distance;
res += "\n" + positionsData.get(0).toString();
//Iterate through the datalist (positionsData).
for (int i = 1; i < positionsData.size(); i++) {
double distance = positionData.uDistance(positionsData.get(i), wifis);
res += "\n" + positionsData.get(i).getName() + "\n" + distance;
res += "\n" + positionsData.get(i).toString();
flagPositionInserted = false;
//Iterate through the sorted list (min_distance_positions).
for (int j = 0; j < min_distance_positions.size(); j++){
if (distance < positionData.uDistance(positionsData.get(min_distance_positions.get(j)), wifis)) {
min_distance_positions.add(j, i);
flagPositionInserted = true;
break;
}
}
if (!flagPositionInserted) {
if (min_distance_positions.size() < POSITIONS_ARRAY_SIZE) {
min_distance_positions.add(i);
}
}
}
//min_distance_positions.size() should be less or equal to 3(POSITIONS_ARRAY_SIZE).
//min_distance_positions.get(0) is the closestPosition.
//min_distance_positions.get(1) is the 2nd closestPosition.
//min_distance_positions.get(2) is the 3rd closestPosition.
String msg = "";
for (int i = 0; i < min_distance_positions.size(); i++){
msg += min_distance_positions.get(i) + ", ";
}
Log.v("Result", "Position ArrayList Content: " + msg);
closestPosition = positionsData.get(min_distance_positions.get(0)).getName();
if (positionData.uDistance(positionsData.get(min_distance_positions.get(0)), wifis) >= PositionData.MAX_DISTANCE){
closestPosition="OUT OF RANGE";
Toast.makeText(this,"You are out of range of the selected building",Toast.LENGTH_LONG).show();
}
result.setText("Nearest point : "+ closestPosition);
res += "\nCurrent:\n" + positionData.toString();
Log.v("Result", res);
closestPosition2 = positionsData.get(min_distance_positions.get(1)).getName();
if (positionData.uDistance(positionsData.get(min_distance_positions.get(1)), wifis) >= PositionData.MAX_DISTANCE){
closestPosition2="OUT OF RANGE";
Toast.makeText(this,"You are out of range of the selected building",Toast.LENGTH_LONG).show();
}
result2.setText("Nearest point : "+ closestPosition2);
closestPosition3 = positionsData.get(min_distance_positions.get(2)).getName();
if (positionData.uDistance(positionsData.get(min_distance_positions.get(2)), wifis) >= PositionData.MAX_DISTANCE){
closestPosition3="OUT OF RANGE";
Toast.makeText(this,"You are out of range of the selected building",Toast.LENGTH_LONG).show();
}
result3.setText("Nearest point : "+ closestPosition3);
代码是使用 INSERTION SORT 来根据点的距离对它们进行排序，并将点的位置存储在另一个ArrayList中（min_distance_positions）。根据样本数据，原始顺序为：d（位置0），a（位置1），f（位置2），b（位置3），c（位置4），e（位置5）。排序顺序为：2（f），3（b），0（d），1（a），4（c），5（e）。 if (min_distance_positions.size() < POSITIONS_ARRAY_SIZE)用于控制输出ArrayList（min_distance_positions）的大小，因此现在味精仅是：2，3，0。如果省略此代码，则味精为：2、3、0、1、4、5，
希望有帮助！
答案 2 :(得分：0)
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
System.out.println("Hello World");
int[] numbers = new int[10];
numbers[0] = 100;
numbers[1] = -34200;
numbers[2] = 3040;
numbers[3] = 400433;
numbers[4] = 500;
numbers[5] = -100;
numbers[6] = -100;
numbers[7] = 532;
numbers[8] = 6584;
numbers[9] = -945;
// my number
int myNumber = 150;
Arrays.sort(numbers);
// for first nearest value
int num = valnearest(numbers, myNumber);
int firstnearestNumber = numbers[num];
System.out.println("firstnearestNumber--->" + firstnearestNumber);
// for Second nearest value
numbers = removeTheElement(numbers, num);
int newnum = valnearest(numbers, myNumber);
int secondnearestNumber = numbers[newnum];
System.out.println("secondnearestNumber--->" + secondnearestNumber);
}
public static int valnearest(int[] numbers, int myNumber) {
int idx = 0;
int lastdistance = -1;
for (int c = 0; c < numbers.length; c++) {
int distance = Math.abs(numbers[c] - myNumber);
if (lastdistance != -1) {
if (distance < lastdistance) {
idx = c;
}
}
lastdistance = distance;
}
return idx;
}
public static int[] removeTheElement(int[] arr,
int index) {
// If the array is empty
// or the index is not in array range
// return the original array
if (arr == null
|| index < 0
|| index >= arr.length) {
return arr;
}
// Create another array of size one less
int[] anotherArray = new int[arr.length - 1];
// Copy the elements except the index
// from original array to the other array
for (int i = 0, k = 0; i < arr.length; i++) {
// if the index is
// the removal element index
if (i == index) {
continue;
}
// if the index is not
// the removal element index
anotherArray[k++] = arr[i];
}
// return the resultant array
return anotherArray;
}
}