uva---10020+贪心
区间覆盖问题,刘汝佳小白书P154页有具体思路;
代码例如以下:
#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> using namespace std; typedef struct { int x,y; }P; P p[110000]; int cmp(P p1,P p2) { if(p1.x==p2.x) return p1.y<p2.y; return p1.x<p2.x; } int main() { int i,j,k,t,m,ans[110000],cnt; scanf("%d",&t); while(t--) { scanf("%d",&m); k=0; while(1) { int x,y; scanf("%d%d",&x,&y); if(!x&&!y) break; p[k].x=x; p[k].y=y; k++; } sort(p,p+k,cmp); cnt=0; int left=0,right,flag=0; for(i=0;i<k;) { right=0; while(p[i].x<=left&&i<k) { if(p[i].y>right) { right=p[i].y; j=i; } i++; } if(right==0) break; left=right; ans[cnt++]=j; if(right>=m) { flag=1; break; } } if(!flag) { printf("0\n"); if(t) printf("\n"); continue; } printf("%d\n",cnt); for(i=0;i<cnt;i++) printf("%d %d\n",p[ans[i]].x,p[ans[i]].y); if(t) printf("\n"); } return 0; }