hdu1677--Nested Dolls（贪心+LIS）-白红宇的个人博客

发布日期：2022-02-02 02:58:14 浏览次数：18 分类：技术文章

本文共 2708 字，大约阅读时间需要 9 分钟。

Problem Description

Dilworth is the world’s most prominent collector of Russian nested dolls: he literally has thousands of them! You know, the wooden hollow dolls of different sizes of which the smallest doll is contained in the second smallest, and this doll is in turn contained in the next one and so forth. One day he wonders if there is another way of nesting them so he will end up with fewer nested dolls? After all, that would make his collection even more magnificent! He unpacks each nested doll and measures the width and height of each contained doll. A doll with width w1 and height h1 will fit in another doll of width w2 and height h2 if and only if w1 < w2 and h1 < h2. Can you help him calculate the smallest number of nested dolls possible to assemble from his massive list of measurements?

Input

On the first line of input is a single positive integer 1 <= t <= 20 specifying the number of test cases to follow. Each test case begins with a positive integer 1 <= m <= 20000 on a line of itself telling the number of dolls in the test case. Next follow 2m positive integers w1, h1,w2, h2, . . . ,wm, hm, where wi is the width and hi is the height of doll number i. 1 <= wi, hi <= 10000 for all i.

Output

For each test case there should be one line of output containing the minimum number of nested dolls possible.

Sample Input

4320 30 40 50 30 40420 30 10 10 30 20 40 50310 30 20 20 30 10410 10 20 30 40 50 39 51

Sample Output

题目大意：

先给出一些盒子，知道其宽w和高h，小盒子可以装到大盒子里边，其条件是w1<w2&&h1<h2，求最多能装几个盒子。

这道题我实在不知道怎么做，看了别人的博客，感觉有点明白，但是没有真正的读懂..................................

代码实现：

#include 
   
    #include
    
     #include
     
      using namespace std;#define N 20005struct node{    int h;    int w;}a[N];int dp[N];int stack[N];int cmp(node a,node b){    if(a.w==b.w)    return a.h
      
       b.w;}int lis(int n){    memset(dp,0,sizeof(dp));    memset(stack,0,sizeof(stack));    int top=0;    stack[top]=-99999999;    int maxx=-1;    for(int i=1; i<=n; i++)    {        if(a[i].h>=stack[top])        {            stack[++top]=a[i].h;            dp[i]=top;        }        else        {            int l=1,r=top;            while(l<=r)            {                int mid=(l+r)/2;                if(a[i].h>=stack[mid])                {                    l=mid+1;                }                else                    r=mid-1;            }            stack[l]=a[i].h;            dp[i]=l;        }        if(dp[i]>maxx)        maxx=dp[i];    }    return maxx;}int main(){    int t,n;    cin>>t;    while(t--)    {        cin>>n;        for(int i=1; i<=n; i++)        {            cin>>a[i].w>>a[i].h;        }        sort(a+1,a+n+1,cmp);        int ans=lis(n);        cout<
       
        <

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