【NOIP考前题目回顾】Luogu P1047

思路

类似前缀和，维护一下差分就好。

代码

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>using namespace std;int a[10005],n,m,ans=0;int main(){    scanf("%d%d",&n,&m);    for (int i=1;i<=m;i++)    {        int x,y;        scanf("%d%d",&x,&y);        a[x]++,a[y+1]--;    }    ans=(a[0]==0);    for (int i=1;i<=n;i++)    {        a[i]+=a[i-1];        if (a[i]==0) ans++;    }    cout<<ans;    return 0;}