ZCMU - 4927: 剩下的树

#include<bits/stdc++.h>#include<cmath>#define mem(a,b) memset(a,b,sizeof a)#define ssclr(ss) ss.clear(), ss.str("")#define INF 0x3f3f3f3f#define MOD 1000000007usingnamespacestd;
typedeflonglongll;
structnode{
intl,r;
}nds[120];
intcmp(noden1,noden2)
{
returnn1.l==n2.l?n1.r<n2.r:n1.l<n2.l;
}
intmain()
{
intn,m,l1,r1,l2,r2,rs;
while(~scanf("%d%d",&n,&m) &&n&&m)
    {
rs=0;
for(inti=0;i<m;i++)
scanf("%d%d",&nds[i].l,&nds[i].r);
sort(nds,nds+m,cmp);
l1=nds[0].l, r1=nds[0].r;
rs+=l1-0;
for(inti=1;i<m;i++)
        {
l2=nds[i].l, r2=nds[i].r;
if(l2<=r1&&r2>r1) r1=r2;
elseif(l2>r1)
            {
rs+=l2-r1-1;
l1=l2;
r1=r2;
            }
        }
rs+=n-r1;
printf("%d\n",rs);
    }
return0;
}