[贪心] BZOJ 3410 [Usaco2009 Dec]Selfish Grazing 自私的食草者

来源：互联网发布：linux 最好用的输入法编辑：程序博客网时间：2024/05/20 17:23

题目大意：取尽量多的区间两两交为空

按照右端点排序然后贪心。因为右端点小显然接下来可以取更多的区间

#include<cstdio>#include<cstdlib>#include<algorithm>using namespace std;inline char nc(){static char buf[100000],*p1=buf,*p2=buf;if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }return *p1++;}inline void read(int &x){char c=nc(),b=1;for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;}const int N=500005;int now,n,ans;struct abcd{int x,y;}a[N];inline bool cmp(abcd a,abcd b){    return a.y<b.y;}int main(){    freopen("t.in","r",stdin);    freopen("t.out","w",stdout);    read(n);    for (int i=1;i<=n;i++) read(a[i].x),read(a[i].y);    sort(a+1,a+n+1,cmp);    now=1;    for (int i=1;i<=n;i++) if(a[i].x>=now)ans++,now=a[i].y;    printf("%d\n",ans);    return 0;}

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