Description Chiaki has n intervals and the i-th of them is [li, ri]. She wants to delete some intervals so that there does not exist three intervals a, b and c such that a intersects with b, b intersects with c and c intersects with a. Chiaki is inte…

Intervals Time Limit: 1 Second      Memory Limit:65536 KB      Special Judge Chiaki has n intervals and thei-th of them is [li,ri]. She wants to delete some intervals so that there does not exist three intervalsa,b andc such thata intersects withb,b…

(-￣▽￣)-* //求一个集合,这个集合与任意一个区间的交集,需至少有两个数字 //贪心过程:按n个区间的最右值从小到大对区间进行排列, //集合首先取第一个区间的最右两个数字, //到第二个区间,判断集合里的数有没有在区间里 //没有的话,就从第二个区间的最右开始往左取(cnt=0取最后两个数,cnt=1取最后一个数) #include<iostream> #include<cstdio> #include<cstring> #include<algorith…

Chiaki has n intervals and the i-th of them is [li, ri]. She wants to delete some intervals so that there does not exist three intervals a, b and c such that a intersects with b, b intersects with c and c intersects with a. Chiaki is interested in th…

题意 有n个区间,要求删除一些区间使得不存在三个相交的区间.找出删除的最少区间. 分析 是个比较显然的贪心吧. 先按照区间的左起点进行排序,然后从左往右扫,当有三个区间相交的时候,删除那个右端点最远的那个区间. 这个想法显然是没错的,但是问题是n最大是50000,我们该怎么在时间复杂度以内边扫边找相交区间呢? 我们可以在从左到右扫的时候维护一个vector,里面是到目前为止,右端点最远的三个区间.我们判断相交是要从这里面判断就可以.当这里面的三个区间相交的时候,根据上面的规则删除,当不想交的时候…

Intervals 题意:给出n个区间,求最少删除多少个区间使得任意三个区间都不相交. 思路:按区间左端点排序,每次选取r最大的两个与当前比较,如果能放更新r,否则删除r最大的.关键就在怎么删除r最大的,我们可以再定义一个排序数组,按r排序即可,然后比较. struct node { int l,r,id; } v[5],a[N]; int b[N]; bool cmp(node x,node y) { if(x.l==y.l) return x.r<y.r; return x.l<y.l;…

动态规划与贪心相关: {HDU}{4739}{Zhuge Liang's Mines}{压缩DP} 题意:给定20个点坐标,求最多有多少个不相交(点也不相交)的正方形 思路:背包问题,求出所有的正方形,然后求最多有多少个正方形不互相覆盖,这题真是神思路. {POJ}{3846}{Mountain Road} 题意:给定两个地点车的班次,路是双向单车道,求安排最短的时间 思路:对车次序列进行二维DP转移,转移的时候需要注意时刻的维护.这个题目的DP思路是正向DP,每次遍历到f[i][j]都需要更新…

Intervals 题目连接: http://codeforces.com/gym/100231/attachments Description 给你n个区间,告诉你每个区间内都有ci个数 然后你需要找一个最小的点集,使得满足这n个区间的条件 Input n 然后li,ri,ci Output 输出最小点集大小 Sample Input 5 3 7 3 8 10 3 6 8 1 1 3 1 10 11 1 Sample Output 6 Hint 题意 题解: 线段树+二分+贪心 首先我们贪心一…

Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 12123   Accepted: 5129 Description An integer interval [a,b], a < b, is a set of all consecutive integers beginning with a and ending with b. Write a program that: finds the minimal number…

Integer Intervals Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 12192   Accepted: 5145 Description An integer interval [a,b], a < b, is a set of all consecutive integers beginning with a and ending with b. Write a program that: finds t…