第2章 数字之魅——区间重合判断

 1 package chapter2shuzizhimei.qujianchonghe;
 2 /**
 3  * 区间重合判断
 4  * @author DELL
 5  *
 6  */
 7 public class IntervalOverlap {
 8     //区间类
 9     public static class Interval{
10         public double x; //区间左端点
11         public double y; //区间右端点
12         public Interval(double x, double y){
13             this.x = x;
14             this.y = y;
15         }
16     }
17     
18     //快速排序的一次划分
19     public static int partition(Interval a[], int b, int e){
20         Interval temp = a[b];
21         while(b<e){
22             while(b<e&&a[e].x>=temp.x)
23                 e--;
24             if(b<e)
25                 a[b] = a[e];
26             while(b<e&&a[b].x<=temp.x)
27                 b++;
28             if(b<e)
29                 a[e] = a[b];
30         }
31         a[b] = temp;
32         return b;
33     }
34     
35     //快速排序
36     public static void quickSort(Interval a[], int b, int e){
37         if(b>=e)
38             return;
39         int i = partition(a, b, e);
40         quickSort(a, b, i-1);
41         quickSort(a, i+1, e);
42     }
43     
44     //区间重合判断
45     public static boolean isOverlap(Interval a[], Interval b){
46         int n = a.length, i,j;
47         quickSort(a, 0, n-1);
48         System.out.println("排序后的区间为：");
49         for(i=0;i<n;i++){
50             System.out.println("["+a[i].x+", "+a[i].y+"] ");
51         }
52         for(i=1,j=0;i<n;i++){
53             if(a[j].y>=a[i].x){
54                 if(a[j].y<=a[i].y){
55                     a[j].y = a[i].y;
56                 }
57             }
58             else{
59                 j++;
60                 a[j] = a[i];  //不能合并区间邻接存放
61             }
62         }
63         System.out.println("合并后的区间为：");
64         for(i=0;i<=j;i++){
65             System.out.println("["+a[i].x+", "+a[i].y+"] ");
66         }
67         for(i=0;i<=j;i++){
68             if(a[i].x<=b.x&&a[i].y>=b.y)
69                 return true;
70         }
71         return false;
72     }
73     public static void main(String[] args) {
74         Interval a[] = new Interval[3];
75         a[0] = new Interval(2,3);
76         a[1] = new Interval(1,2);
77         a[2] = new Interval(3,9);
78         Interval a1 = new Interval(1,6);
79         boolean b = isOverlap(a,a1);
80         if(b){
81             System.out.println("区间重合！");
82         }else{
83             System.out.println("区间不重合！");
84         }
85 
86     }
87 
88 }

排序后的区间为：
[1.0, 2.0] 
[2.0, 3.0] 
[3.0, 9.0] 
合并后的区间为：
[1.0, 9.0] 
区间重合！