Colidity-- NumberOfDiscIntersections

先对区间左边界排序，在对右边界左二分查找
 1 // you can use includes, for example:
 2 #include <algorithm>
 3 
 4 // you can write to stdout for debugging purposes, e.g.
 5 // cout << "this is a debug message" << endl;
 6 class node
 7 {
 8     public:
 9         int left;
10         int right;
11         node(int l,int r):left(l),right(r){}
12         bool operator<(const node &other)const
13         {
14             if(left < other.left)
15             {
16                 return true;
17             }
18             else if(left > other.left)
19             {
20                 return false;
21             }
22             else
23             {
24                 return right<=other.right;
25             }
26         }
27 };
28 int binary_ser(const vector<node> &v,int s,int e,int target)
29 {
30     while(s <= e)
31     {
32         int mid = s+(e-s)>>1;
33         if(v[mid].left == target)
34         {
35             return mid;
36         }
37         else if(v[mid].left > target)
38         {
39             e = mid-1;
40         }
41         else
42         {
43             s = mid+1;
44         }
45     }
46     return s;
47 }
48 int solution(vector<int> &A) {
49     // write your code in C++11
50     vector<node> v;
51     for(int i = 0 ; i < A.size() ; ++i)
52     {
53         v.push_back(node(i-A[i],i+A[i]));
54     }
55     sort(v.begin(),v.end());
56     int res = 0;
57     for(int j = 0 ; j < v.size() ; ++j)
58     {
59         int tmp = binary_ser(v,j+1,v.size()-1,v[j].right);
60         res += tmp-j-1;
61     }
62     return res;
63 }