Snapchat - ColorSum

给一些RGB的点，比如(86, 5, 211),  (128, 99, 5), 再一个target点，看使用这些给的点能不能叠加得到target，每个点只能用一次

就是最基本的backtracking

 1 public class ColorSum {
 2     static class Color {
 3         int r;
 4         int g;
 5         int b;
 6         public Color(int r, int g, int b) {
 7             this.r = r;
 8             this.g = g;
 9             this.b = b;
10         }
11         
12         public void add(Color color) {
13             this.r = (this.r + color.r > 255)? 255: (this.r + color.r);
14             this.g = (this.g + color.g > 255)? 255: (this.g + color.g);
15             this.b = (this.b + color.b > 255)? 255: (this.b + color.b);
16         }
17         
18         public boolean substract(Color color) {
19             if(color.r > this.r || color.g > this.g || color.b > this.b) {
20                 return false;
21             }
22             this.r = this.r - color.r;
23             this.g = this.g - color.g;
24             this.b = this.b - color.b;
25             return true;
26         }
27         
28         public boolean equalsZero() {
29             return r == 0 && g == 0 && b == 0;
30         }
31         
32         public String toString() {
33             return "(" + r + ", " + g + ", " + b + ")";
34         }
35     }
36     
37     public boolean canSum(List<Color> colors, Color target) {
38         if(colors == null || colors.size() == 0 || target == null) {
39             return false;
40         }
41         return helper(colors, 0, target);
42     }
43     
44     private boolean helper(List<Color> colors, int index, Color target) {
45         if(target.equalsZero()) {
46             return true;
47         }
48         for(int i = index; i < colors.size(); i++) {
49             if(target.substract(colors.get(i))) {
50                 if(helper(colors, i + 1, target)) {
51                     return true;
52                 }
53                 target.add(colors.get(i));
54             }
55         }
56         return false;
57     }
58     
59     public static void main(String[] args) {
60         ColorSum sample = new ColorSum();
61         List<Color> colors = new ArrayList<>();
62         colors.add(new Color(86, 5, 211));
63         colors.add(new Color(128, 99, 5));
64         colors.add(new Color(92, 25, 6));
65         colors.add(new Color(16, 45, 4));
66         Color target = new Color(236, 169, 15);
67         System.out.println(sample.canSum(colors, target));
68     }
69 }

 

posted @ 2016-10-11 04:47  warmland  阅读(384)  评论(0)    收藏  举报