Codeforces 4D D. Mysterious Present (DP)

Topic Connection:

Codeforces 4D

Main topic:

Give n envelopes, the N envelopes are long and wide, give the size of the card, find the longest sequence that can be loaded into the card, the length and width of the sequence satisfies the last, the longest, and give a set of feasible solutions.

Topic Analysis:

• This topic is the topic of DP, the state definition dp[i] is the maximum length of the sequence ending with I, and the path of the optimal solution is obtained by using an array record, which is stored in the form of a chain list.
• First, the given envelopes are sorted, according to the width of the first keyword, high as the second keyword,
• The state transition equation is as follows: d P[I]= Max j = Span class= "mn" id= "mathjax-span-2310" style= "font-size:70.7%; Font-family:mathjax_main; " >0 J? 1 {d P[J]+1},{a[J].W<a[I].W && a[J].h<a[I].h}
• The answer is returned recursively in reverse order.
  

AC Code:

#include <iostream>#include <cstring>#include <cstdio>#include <algorithm>#define MAX 5007using namespace STD;intN,w,h;intDp[max];intBack[max];structnode{intW,h,x;BOOL operator< (ConstNode & A)Const{if(w = = A.W)returnH < a.h;returnW < A.W; }}a[max];voidPrint (intx) {if(A[x]. W <= W | | a[x].h <= h)return; Print (back[x]);printf("%d", a[x].x);}intMain () { while( ~scanf("%d%d%d", &n, &w, &h)) { for(inti =1; I <= N; i++) {scanf("%d%d", &AMP;A[I].W, &a[i].h);        a[i].x = i; } dp[0] = -1; Sort (A +1, a+n+1); for(inti =1; I <= N; i++) {inttemp =-1, id =0; for(intj =0; J < I; J + +)if(A[J].W < A[I].W && A[j].h < a[i].h && a[j].w > W && a[j].h > H)if(Temp < DP[J])                        {temp = Dp[j];                    id = j; }if(A[i].w > W && a[i].h > H) dp[i] =1, back[i] =0;ElseDp[i] =-1;if(temp+1> Dp[i]) {Dp[i] = temp+1;            BACK[I] = ID; }        }intMAXN =0; for(inti =1; I <= N; i++) MAXN = max (MAXN, Dp[i]);if(MAXN = =0)        {puts("0");Continue; }printf("%d\n", MAXN); for(inti =1; I <= N; i++)if(MAXN = = Dp[i]) {print (i);puts(""); Break; }    }}

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Codeforces 4D D. Mysterious Present (DP)