335. Self Crossing

    /*
     * 335. Self Crossing
     * 2016-7-10 by Mingyang
     */
    // Categorize the self-crossing scenarios, there are 3 of them: 
    // 1. Fourth line crosses first line and works for fifth line crosses second line and so on...
    // 2. Fifth line meets first line and works for the lines after
    // 3. Sixth line crosses first line and works for the lines after
    public boolean isSelfCrossing(int[] x) {
        int l = x.length;
        if(l <= 3) return false;
        
        for(int i = 3; i < l; i++){
            if(x[i] >= x[i-2] && x[i-1] <= x[i-3]) return true;  //Fourth line crosses first line and onward
            if(i >=4)
            {
                if(x[i-1] == x[i-3] && x[i] + x[i-4] >= x[i-2]) return true; // Fifth line meets first line and onward
            }
            if(i >=5)
            {
                if(x[i-2] - x[i-4] >= 0 && x[i] >= x[i-2] - x[i-4] && x[i-1] >= x[i-3] - x[i-5] && x[i-1] <= x[i-3]) return true;  // Sixth line crosses first line and onward
            }
        }
        return false;
    }