POJ 1321 Checkerboard Issues (DFS + backtracking)

Title Link: http://poj.org/problem?id=1321

Test instructions: Chinese topic, not much to say ...

Ideas:

There are many ways to solve the problem, just start thinking is to choose from N rows containing the "#" K line, and then put K in this K-line pieces, just fine. The time complexity is O (C (n, k) * k!), when the real writing is actually used 2N * k!, reluctantly too. Later thought can start from the first occurrence of the "#" search, after searching to jump directly to the next line to continue, you do not have to do the first time so troublesome.

Code:

(1)

1#include <iostream>2#include <cmath>3#include <cstdio>4#include <cstring>5#include <cstdlib>6#include <stack>7#include <queue>8#include <vector>9#include <algorithm>Ten#include <string> One  AtypedefLong LongLL; - using namespacestd; - Const intMAXN =8; the intMAP[MAXN +3][MAXN +3]; - intROW[MAXN +3]; - intCHOSE[MAXN +3]; - intN, K; + intans; -  + voidChessdfs (intt) { A     if(T >k) { at++ans; -     } -     Else { -         intCNT =0; -          for(inti =1; I <= N; i++) {//from 1 to n rows, locate the row where the first T piece is placed.  -             if(Chose[i]) + +CNT; in             if(cnt = = T &&Chose[i]) { -                  for(intj =1; J <= N; J + +) {//look for "#" in the line to                     if(Map[i][j] = ='#'&& Row[j] = =0) { +Chose[i] = j;//The first t piece is placed in the J position of line I -ROW[J] =1; theChessdfs (t +1); *ROW[J] =0; $                     }Panax Notoginseng                 } -             } the         } +     } A } the  + intCheckintk) { -      for(inti =1; I <= N; i++) { $         if(Map[k][i] = ='#'&& Chose[k])return 1; $     } -     return 0; - } the  - voidLinedfs (intt) {Wuyi     if(T >N) { the         intCNT =0; -          for(inti =1; I <= N; i++) { Wu             if(check (i)) cnt++;//determine the number of 1 in the chose array, and also determine if the selected line contains "#", while satisfying is really selected -         } About         if(cnt = = k) {//indicates that K row is selected and is eligible $memset (Row,0,sizeof(Row)); -Chessdfs (1);//put the K-pieces in the K-line that has been selected -         } -     } A     Else { +          for(inti =0; I <2; i++) {//each row has two states, select and not selected theChose[t] = i;//Chose[t] = 1 is selected for line T -Linedfs (t +1); $         } the     } the } the  the intMain () { -      while(SCANF ("%d%d", &n, &k) = =2&& (n! =-1&& k! =-1)) { inmemset (Map,'!',sizeof(map)); thememset (Row,0,sizeof(Row)); the          for(inti =1; I <= N; i++) { About GetChar (); the              for(intj =1; J <= N; J + +) { theMAP[I][J] =GetChar (); the             } +         } -Ans =0; theLinedfs (1);//Select K rows from n rowsBayiprintf"%d\n", ans); the     } the     return 0; -}

POJ 1321 Checkerboard Issues (DFS + backtracking)