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  • Solution of NumberOfDiscIntersections by Codility

    question:https://codility.com/programmers/lessons/4


    this question is seem like line intersections question. we can use similar method to solve this question. 

    now i prove this solution. for each line, it has two endpoint. we call it left and right. assume that  the left and right have been sorted . 

    if line i and line j intersection, we can conclude that left[i]<right[j] or left[j]<right[i]. ...  how to say?

    ?

     

    trap: int overflow


    code:

    #include <algorithm>
    int solution(vector<int> &A) {
        // write your code in C++11
        int size = A.size();
        if (size <2)
            return 0;
        vector<long> begin;
        vector<long> end;
        for(int i=0; i<size; i++){
            begin.push_back(i-static_cast<long>(A[i]));
            end.push_back(i+static_cast<long>(A[i]));
        }
        sort(begin.begin(),begin.end());
        sort(end.begin(),end.end());
        int res = 0;
        int upper_index =0, lower_index=0;
        for(upper_index =0; upper_index<size; upper_index++){
            while(lower_index<size && begin[lower_index]<= end[upper_index])
                lower_index++;
            res += lower_index-upper_index-1;
            if (res >10000000)
                return -1;
        }
        return res;
    }


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  • 原文地址:https://www.cnblogs.com/gccbuaa/p/6755414.html
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