HDU5203

hdu5203.cpp

#include <cstdio>
#include <ctime>
#include <cstdlib>
#include <iostream>
#include <cstring>
#include <vector>
#include <fstream>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <string>
#define MAX(a,b) (a>b?a:b)
#define sd(x) scanf("%d",&x)
#define sdd(a,b) scanf("%d%d",&a,&b)
#define sddd(a,b,c) scanf("%d%d%d",&a,&b,&c)
#define slflf(x,y) scanf("%lf%lf",&x,&y)
#define abs(x) (x<0?(-x):x)
#define MAX(a,b) (a>b?a:b)
#define MIN(a,b) (a<b?a:b)
using namespace std;

int length[3];

long long calcSegment(int len)
{
    long long ret = 0;
    if (len%2==0)
    {
        for (int i = 1;i<len/2;i++)
        {
            ret+=(i-1);
        }
    }
    else
    {
        for (int i=1;i<len/2+1;i++)
        {
            ret+=i;
        }
    }

    return ret;
}


int main()
{
    int n,m,tmp;
    while(~sdd(n,m))
    {
        int leftCut=100000000,rightCut=0;
        for (int i=0; i<m; i++)
        {
            sd(tmp);
            if (tmp>rightCut) rightCut=tmp;
            if (tmp-1<leftCut) leftCut=tmp-1;
        }
        long long cnt =0 ;
        if (leftCut != 0 && rightCut != n)
        {
            for (int i=1; i<n; i++)
            {
                if (i <= rightCut && i >= leftCut) continue;
                if (i < leftCut)
                {
                    length[0]=i;
                    length[1]=leftCut-i;
                    length[2]=n-rightCut;
                }
                else
                {
                    length[0]=leftCut;
                    length[1]=i-rightCut;
                    length[2]=n-i;
                }
                if (length[0]+length[1]>length[2] && \
                        length[1]+length[2]>length[0] && \
                        length[0]+length[2]>length[1])
                {
                    cnt++;
                }

            }
        }
        else if (leftCut == 0 && rightCut == n)
        {
            cnt=0;
        }
        else
        {
            cnt = calcSegment(n-rightCut+leftCut);
        }
        cout << cnt << endl;
    }
    return 0;
}