为什么我的线段交叉测试不返回 true？

我已经知道这个程序的输出应该是什么了——我的问题是我无法让程序给出正确的输出，或者任何输出。我的问题是：识别并显示给定巡回赛中与任何其他腿交叉的所有腿。数据如下：旅游（"城市"）为{0，4，1，3，2}，这些"城市"的点为{2,0}，{4,1}，{0,1}，{3,2}，{1,2}。这是我的程序：

    #include <iostream>
    using namespace std;
    const int MAX = 100;
    bool doCross(int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4);
    int main()
    {
        int numPts = 5;
        int tourAry[MAX] = {0, 4, 1, 3, 2};
        int pointsAry[MAX][2] = {{2, 0},{4, 1},{0, 1},{3, 2},{1, 2}};

        for(int start = 0; start <= numPts - 3; start++)
        {
            int startPt = tourAry[0];
            int endPt = tourAry[1];
            int testSegmentX1 = pointsAry[startPt][0];
            int testSegmentY1 = pointsAry[startPt][1];
            int testSegmentX2 = pointsAry[endPt][0];
            int testSegmentY2 = pointsAry[endPt][1];
            for(int nextSeg = start + 2; nextSeg <= numPts - 2; nextSeg++)
            {
                startPt = tourAry[2];
                endPt = tourAry[3];
                int startX = pointsAry[startPt][0];
                int startY = pointsAry[startPt][1];
                int endX = pointsAry[endPt][0];
                int endY = pointsAry[endPt][1];
                if(doCross(testSegmentX1, testSegmentY1, testSegmentX2, testSegmentY2, startX, startY, endX, endY))
                {
                    cout << tourAry[start] << " - " << tourAry[start+1] << " crosses " << tourAry[nextSeg] << " - " << tourAry[nextSeg+1] << endl;
                }
            }//for
        }//for
        return 0;
    }//main
    bool doCross(int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4)
    {
        bool cross = true;
        double denom, numerA, numerB, uA, uB;

        denom = ((y4 - y3) * (x2 - x1)) - ((x4 - x3) * (y2 - y1));
        numerA = ((x4 - x3) * (y1 - y3)) - ((y4 - y3) * (x1 - x3));
        numerB = ((x2 - x1) * (y1 - y3)) - ((y2 - y1) * (x1 - x3));
        if(denom == 0.0)
        {
            if(numerA == 0.0 && numerB == 0.0)
            {
                cross = false;
            }//if
        }//if
        else
        {
            float uA = numerA / denom;
                    float uB = numerB / denom;
            if (uA > 0.0 && uA < 1.0 && uB > 0.0 && uB < 1.0)
            {
                cross = true;
            }//if
            else
            {
                cross = false;
            }//else
        }//else
        return cross;
    }//doCross

我知道输出应该是：0-4传3-24-1越过3-2

如有任何帮助，我们将不胜感激。