I have tried all test cases i could think of but i am not able to find why it is giving wrong answer.please help.

#include<iostream>
using namespace std;
int main()
{
    int t,b,i,k;
    cin>>t;
    while(t--)
    {
        int len=0;
        int q[10][2];
        int r[501];
        for(i=0;i<501;i++)
            r[i]=0;
        for(i=0;i<10;i++)
            for(int j=0;j<2;j++)
                q[i][j]=0;
        cin>>b;
        int s,e,l;
        for(i=0;i<b;i++)
        {
            cin>>s>>e>>l;
            q[l][0]=s;
            q[l][1]=e;
        }
        for(i=0;i<9;i++)
        {
            if(q[i][0]==0 && q[i+1][0]==0)
                continue;
            if(q[i][1]>=q[i+1][0] && q[i][1]<=q[i+1][1] && q[i][0]<q[i+1][0])
            {
                for(k=q[i+1][0];k<=q[i][1];k++)
                    if(r[k]==0)
                    {
                        len++;
                        r[k]=1;
                    }
            }
            else if(q[i+1][0]>=q[i][0] && q[i+1][0]<=q[i][1] && q[i+1][1]>q[i][1])
            {
                for(k=q[i][1];k<=q[i+1][0];k++)
                    if(r[k]==0)
                    {
                        len++;
                        r[k]=1;
                    }
            }
            else if(q[i][0]<=q[i+1][0] && q[i][1]>=q[i+1][1])
            {
                for(k=q[i+1][0];k<=q[i+1][1];k++)
                    if(r[k]==0)
                    {
                        len++;
                        r[k]=1;
                    }
            }
            else if(q[i][0]>=q[i+1][0] && q[i][1]<=q[i+1][1])
            {
                for(k=q[i][0];k<=q[i][1];k++)
                    if(r[k]==0)
                    {
                        len++;
                        r[k]=1;
                    }
            }
        }
        cout<<500-len<<endl;
    }
    return 0;
}