Colidity-- NumberOfDiscIntersections

先对区间左边界排序，在对右边界左二分查找

// you can use includes, for example:
#include <algorithm>

// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
class node
{
    public:
        int left;
        int right;
        node(int l,int r):left(l),right(r){}
        bool operator<(const node &other)const
        {
            if(left < other.left)
            {
                return true;
            }
            else if(left > other.left)
            {
                return false;
            }
            else
            {
                return right<=other.right;
            }
        }
};
int binary_ser(const vector<node> &v,int s,int e,int target)
{
    while(s <= e)
    {
        int mid = s+(e-s)>>1;
        if(v[mid].left == target)
        {
            return mid;
        }
        else if(v[mid].left > target)
        {
            e = mid-1;
        }
        else
        {
            s = mid+1;
        }
    }
    return s;
}
int solution(vector<int> &A) {
    // write your code in C++11
    vector<node> v;
    for(int i = 0 ; i < A.size() ; ++i)
    {
        v.push_back(node(i-A[i],i+A[i]));
    }
    sort(v.begin(),v.end());
    int res = 0;
    for(int j = 0 ; j < v.size() ; ++j)
    {
        int tmp = binary_ser(v,j+1,v.size()-1,v[j].right);
        res += tmp-j-1;
    }
    return res;
}