我有一系列正/负的整数
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;
现在,我想针对这个数组测试另一个int,并返回最接近int的数字。
例如,如果我使用数字490
,我会从数字500
返回第4项,这样做的最佳方法是什么?
int myNumber = 490;
int distance = 0;
int idx = 0;
for(int c = 0; c < numbers.length; c++){
int cdistance = numbers[c] - myNumber;
if(cdistance < distance){
idx = c;
distance = cdistance;
}
}
int theNumber = numbers[idx];
这不起作用。有关一个好方法的任何建议吗?
答案 0 :(得分:38)
int myNumber = 490;
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 theNumber = numbers[idx];
始终使用您正在考虑的第一个元素初始化您的最小/最大函数。使用诸如Integer.MAX_VALUE
或Integer.MIN_VALUE
之类的东西是获得答案的天真方式;如果您稍后更改数据类型(哎呀,MAX_LONG
和MAX_INT
非常不同!)或者您将来想要编写通用min/max
方法,它就不会很好用对于任何数据类型。
答案 1 :(得分:9)
在 Java 8 :
中List<Integer> list = Arrays.stream(numbers).boxed().collect(Collectors.toList());
int n = 490;
int c = list.stream()
.min(Comparator.comparingInt(i -> Math.abs(i - n)))
.orElseThrow(() -> new NoSuchElementException("No value present"));
最初,您可以使用List
代替Array
(列表具有更多功能)。
答案 2 :(得分:4)
答案 3 :(得分:2)
cdistance = numbers[c] - myNumber
。你没有采取差异的绝对值。如果myNumber
远大于numbers[c]
或numbers[c]
为负数,则比较将注册为“最小差异”。
以numbers[c] = -34200
为例。 numbers[c] - myNumber
将为-34690,远低于distance
。
此外,您应该将distance
初始化为较大的值,因为在开始时未找到任何解决方案。
答案 4 :(得分:1)
一个语句块初始化并设置最接近的匹配。此外,如果找不到最接近的匹配,则返回-1(空数组)。
protected int getClosestIndex(final int[] values, int value) {
class Closest {
Integer dif;
int index = -1;
};
Closest closest = new Closest();
for (int i = 0; i < values.length; ++i) {
final int dif = Math.abs(value - values[i]);
if (closest.dif == null || dif < closest.dif) {
closest.index = i;
closest.dif = dif;
}
}
return closest.index;
}
答案 5 :(得分:1)
int valueToFind = 490;
Map<Integer, Integer> map = new HashMap();
for (int i = 0, i < numbers.length; i++){
map.put(Math.abs(numbers[i] - valueToFind), numbers[i]);
}
List<Integer> keys = new ArrayList(map.keySet());
Collections.sort(keys);
return map.get(keys.get(0));
答案 6 :(得分:0)
我这样做是为了我的课程作业,我把它编程为Ready to Program Java,很抱歉,如果它有点令人困惑。
// The "Ass_1_B_3" class.
import java.awt.*;
import hsa.Console;
public class Ass_1_B_3
{
static Console c; // The output console
public static void main (String[] args)
{
c = new Console ();
int [] data = {3, 1, 5, 7, 4, 12, -3, 8, -2};
int nearZero = 0;
int temp = 0;
int temp2 = data[0];
for (int i = 0; i < data.length; i++)
{
temp = Math.abs (data[i]);
nearZero = temp2;
if (temp < temp2)
{
temp2 = temp;
nearZero = data[i];
}
}
c.println ("The number closest to zero is: " + nearZero);
// Place your program here. 'c' is the output console
} // main method
} // Ass_1_B_3 class
答案 7 :(得分:0)
public int getClosestToTarget(int target, int[] values) {
if (values.length < 1)
throw new IllegalArgumentException("The values should be at least one element");
if (values.length == 1) {
return values[0];
}
int closestValue = values[0];
int leastDistance = Math.abs(values[0] - target);
for (int i = 0; i < values.length; i++) {
int currentDistance = Math.abs(values[i] - target);
if (currentDistance < leastDistance) {
closestValue = values[i];
leastDistance = currentDistance;
}
}
return closestValue;
}
答案 8 :(得分:0)
您可以调整旧的二进制搜索并有效地实现它。
Arrays.sort(numbers);
nearestNumber = nearestNumberBinarySearch(numbers, 0, numbers.length - 1, myNumber);
private static int nearestNumberBinarySearch(int[] numbers, int start, int end, int myNumber) {
int mid = (start + end) / 2;
if (numbers[mid] == myNumber)
return numbers[mid];
if (start == end - 1)
if (Math.abs(numbers[end] - myNumber) >= Math.abs(numbers[start] - myNumber))
return numbers[start];
else
return numbers[end];
if(numbers[mid]> myNumber)
return nearestNumberBinarySearch(numbers, start,mid, myNumber);
else
return nearestNumberBinarySearch(numbers,mid, end, myNumber);
}
答案 9 :(得分:0)
科特琳很有帮助
fun List<Int>.closestValue(value: Int) = minBy { abs(value - it) }
val values = listOf(1, 8, 4, -6)
println(values.closestValue(-7)) // -6
println(values.closestValue(2)) // 1
println(values.closestValue(7)) // 8
列表无需进行顺便说一句
答案 10 :(得分:0)
Kotlin - TreeSet
lower
方法返回此中最大的元素
设置严格小于给定元素,如果没有这样的元素,则为 null
元素。
import java.util.*
fun printLowest(number: Int) {
val numbers = listOf(100, 90, 50, -100, -200, 532, 6584, -945)
val lower = TreeSet(numbers).lower(number)
println(lower)
}
printLowest(100) // Prints 90
答案 11 :(得分:-1)
public int nearnum(int myNumber,int[] numbers)
{
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;
}
}
return numbers[idx];
}
答案 12 :(得分:-1)
public class Main
{
public static void main(String[] args)
{
int[] numbers = {6,5,10,1,3,4,2,14,11,12};
for(int i =0; i<numbers.length; i++)
{
sum(numbers, i, numbers[i], 12, String.valueOf(numbers[i]));
}
}
static void sum(int[] arr, int i, int sum, int target, String s)
{
int flag = 0;
for(int j = i+1; j<arr.length; j++)
{
if(arr[i] == target && flag==0)
{
System.out.println(String.valueOf(arr[i]));
flag =1;
}
else if(sum+arr[j] == target)
{
System.out.println(s+" "+String.valueOf(arr[j]));
}
else
{
sum(arr, j, sum+arr[j], target, s+" "+String.valueOf(arr[j]));
}
}
}
}
答案 13 :(得分:-6)
这是我做过的事情......
import javax.swing.JOptionPane;
public class NearestNumber {
public static void main(String[] arg)
{
int[] array={100,-3420,3040,400433,500,-100,-200,532,6584,-945};
String myNumberString =JOptionPane.showInputDialog(null,"Enter the number to test:");
int myNumber = Integer.parseInt(myNumberString);
int nearestNumber = findNearestNumber(array,myNumber);
JOptionPane.showMessageDialog(null,"The nearest number is "+nearestNumber);
}
public static int findNearestNumber(int[] array,int myNumber)
{
int min=0,max=0,nearestNumber;
for(int i=0;i<array.length;i++)
{
if(array[i]<myNumber)
{
if(min==0)
{
min=array[i];
}
else if(array[i]>min)
{
min=array[i];
}
}
else if(array[i]>myNumber)
{
if(max==0)
{
max=array[i];
}
else if(array[i]<max)
{
max=array[i];
}
}
else
{
return array[i];
}
}
if(Math.abs(myNumber-min)<Math.abs(myNumber-max))
{
nearestNumber=min;
}
else
{
nearestNumber=max;
}
return nearestNumber;
}
}