[Algorithm] Programmers :: 우박수열 정적분

https://school.programmers.co.kr/learn/courses/30/lessons/134239

프로그래머스

vector<double> solution(int k, vector<vector<int>> ranges)
{
    vector<double> answer;
    vector<vector<int>> coordinates;
    vector<double> areas = { 0 };
    int count = 0;
    coordinates.push_back({ 0,k });
    
 
    while (k != 1)
    {
        if (k % 2 == 0) k /= 2;
        else k = k * 3 + 1;
 
        ++count;
        coordinates.push_back({ count,k });
    }
 
    double sum = 0;
    for (int i = 1; i < coordinates.size(); ++i)
    {
        int leftX = coordinates[i - 1][0];
        int leftY = coordinates[i - 1][1];
        int rightX = coordinates[i][0];
        int rightY = coordinates[i][1];
 
        double boxArea = min(leftY, rightY) * (rightX - leftX);
        double triangle = abs(rightY - leftY) * (rightX - leftX) / 2.0f;
 
        sum += boxArea + triangle;
        areas.push_back(sum);
    }
 
    int maxX = coordinates.size() - 1;
 
    for (int i = 0; i < ranges.size(); ++i)
    {
        int leftX = ranges[i][0];
        int rightX = maxX + ranges[i][1];
 
        if (leftX > rightX) answer.push_back(-1);
        else answer.push_back(areas[rightX] - areas[leftX]);
    }
 
    return answer;
}