1.CONCEPTION:It will help you easier to finish to use the built-in functions.

2. I use the built-functions such as sort and my own functions such as cmp which is a comparation for sort.

3.

      here are the part of my code.

    sort(arr,arr+n,cmp);//arr is a name of an array, n is the amount of each case.

    int cmp(int a,int b);