uva10318 Security Panel (dfs+ pruning)

Test instructions

There is a r*c on the matrix to select some lattice for "light" operation, so that the final lattice is "bright" state. All the squares above the initial matrix are dark, from top left to bottom, numbering starts at 1.
Now let's give a 3*3 matrix, as a button rule:
For example:
**.
.*.
*..
That is, you press any button, the button as the center of the 3*3 Matrix, according to this rule, that is, press a button, the button around the position of the *, according to the rule, the state changes (if it is not already on a line is ignored)

Give the r,c a few rows of columns
Then give a fixed 3*3 matrix that represents the rules of the button
Ask at least which buttons are pressed to make all the buttons light.

Ideas:

A deep search solution with a straight line. The status of each button is only two lit and not lit.
But there are at most 2^25 states, or very large.
So there needs to be a pruning, that is, you have traversed to line X, if the X-2 line has a button that is not bright, then exit directly, because a button at most affect it on the line, the last two lines are not bright will never light.

AC Code

#include <cstdio>#include <cstring>using namespace STD;Const intINF =0x3f3f3f3f;Const intDx[] = {-1,-1,-1,0,0,0,1,1,1};Const intDy[] = {-1,0,1,-1,0,1,-1,0,1};Const intN =5;CharStr[n];intpattern[3][3], grid[n][n];intR, C, MINV, ans[ -], pressed[ -];intState[n][n];BOOLCheckintx) {if(X <0)return true; for(inti =0; I <= x; i++) { for(intj =0; J < C; J + +) {if(!state[i][j])return false; }    }return true;}voidFuncintXintY) {intNX, NY; for(inti =0; I <9; i++) {if(pattern[1+dx[i]][1+dy[i]] {NX = X+dx[i], NY = y+dy[i];if(NX <0|| NX >= R | | NY <0|| NY >= C)Continue;        State[nx][ny] =!state[nx][ny]; }    }}voidDfsintXintYintcur) {if(y = = c) {if(x = = R1&& check (x)) {if(Minv > cur) {MINV = cur;memcpy(ANS, pressed,sizeof(ans)); }        }Else if(X < R1&& Check (X-2) {DFS (x+1,0, cur); }return; }//selectPressed[cur] = x*c + y +1;    Func (x, y); DFS (x, y+1, cur+1); Func (x, y);//unselectDFS (x, y+1, cur);}intMain () {//Freopen ("In.txt", "R", stdin);    intCAS =1; while(scanf("%d%d", &r, &c)! = EOF && (R | | c)) {//init        memset(State,0,sizeof(state)); for(inti =0; I <3; i++) {scanf('%s ', &AMP;STR); for(intj =0; J <3; J + +) {Pattern[i][j] = (str[j] = =' * ');        }} MINV = INF; Dfs0,0,0);printf("Case #%d\n", cas++);if(MINV! = INF) {printf("%d", ans[0]); for(inti =1; i < MINV; i++) {printf("%d", Ans[i]); }puts(""); }Else{printf("impossible.\n"); }    }return 0;}

uva10318 Security Panel (dfs+ pruning)