Section 1.3 Barn Reapir

贪心算法，思路不难但在提交过程中发现很多bug:
1.得到需要“切板”的位置后，应该按num排序
2.当M == 1时要特别处理，否则number为空向量，程序异常退出
3.输入牛的位置是无序的，要先按num升序排序
4.当M > C的时候，number个数应该为min（M,C）

/*ID: alexyua2PROG: barn1LANG: C++*/#include<fstream>#include<vector>#include<algorithm>using namespace std;ifstream fin("barn1.in");ofstream fout("barn1.out");//ifstream fin("in.txt");//ofstream fout("out.txt");struct Stall{    int num;    int interval;};bool cmp1(Stall a,Stall b){    return a.interval > b.interval;}bool cmp2(Stall a,Stall b){    return a.num < b.num;}bool cmp3(int a,int b){    return a<b; }int main(){    //input    int M,S,C;    fin>>M >>S >>C;    vector<Stall>cows;    int i;    for(i=0;i<C;i++)    {        Stall temp;        fin>>temp.num;        cows.push_back(temp);    }    //BUG 3:the input is arbitory order of the num    sort(cows.begin(),cows.end(),cmp2);       //compute the interval    for(i=0;i<C-1;i++)        cows[i].interval = cows[i+1].num - cows[i].num;    //sort by the interval    sort(cows.begin(),cows.end(),cmp1);    //store M stalls' num where need cutting    vector<int>number;    //BUG 2    if(M == 1)        number.push_back(0);    else    {        int loop = min(M,C); //BUG 4        for(i=0;i<loop-1;i++)        {               number.push_back(cows[i].num);        }    }    //sort by the num    sort(cows.begin(),cows.end(),cmp2);    //BUG 1    sort(number.begin(),number.end(),cmp3);    //greedy algorithm    int beg = cows[0].num,end = cows[0].num;    int result = 0,j=0;    for(i=0;i<C;i++)    {        if(cows[i].num == number[j])        {            end = cows[i].num;            result += end - beg + 1;            beg = cows[i+1].num;            j++;        }        if(j == M-1)            break;    }    end = cows[C-1].num;    result += end - beg + 1;    fout<<result <<endl;    //close files    fin.close();    fout.close();    return 0;}