7-15 Square Destroyer 破坏正方形 uva1603

先是处理所有的正方形 从边长为1开始 将其边存好 满边存好

然后不断扫描正方形  并且进行拆除  直到拆完或者 步数小于等于9（启发方程  因为n小于等于5  九次足以将所有的拆完）

代码实施有很多细节  lrj的代码非常巧妙  ！

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<algorithm>

using namespace std;

const int maxs = ; // number of squares: 25+16+9+4+1=55

const int maxm = ; // number of matches: 2*5*(5+1)=60

int n, exists[maxm]; // matches

int s, size[maxs], fullsize[maxs], contains[maxs][maxm]; // squares

int best;

inline int row_match(int x, int y) {

  return (*n+)*x+y;

}

inline int col_match(int x, int y) {

  return (*n+)*x+n+y;

}

// number of matches in a full n*n grid

inline int match_count(int n) {

  return *n*(n+);

}

void init() {

  int m, v;

  scanf("%d%d", &n, &m);

  for(int i = ; i < match_count(n); ++i) exists[i] = ;

  while(m--) {

    scanf("%d", &v);

    exists[v-] = ;

  }

  // collect full squares

  s = ;

  memset(contains, , sizeof(contains));

  for(int i = ; i <= n; i++) // side length

    for(int x = ; x <= n-i; x++)

      for(int y = ; y <= n-i; y++) {

        size[s] = ;

        fullsize[s] = *i; // number of matches in a complete square

        for(int j = ; j < i; j++) {

          int a = row_match(x, y+j); // up

          int b = row_match(x+i, y+j); // down

          int c = col_match(x+j, y); // left

          int d = col_match(x+j, y+i); // right

          contains[s][a] = ;

          contains[s][b] = ;

          contains[s][c] = ;

          contains[s][d] = ;

          size[s] += exists[a] + exists[b] + exists[c] + exists[d]; // number of matches now

        }

        ++s;

      }

}

int find_square() {

  for(int i = ; i < s; i++)

    if(size[i] == fullsize[i]) return i;

  return -;

}

void dfs(int dep) {

  if(dep >= best) return;

  int k = find_square();

  if(k == -) {

    best = dep;

    return;

  }

  // remove a match in that square

  for(int i = ; i < match_count(n); i++)

    if(contains[k][i]) {

      for(int j = ; j < s; j++)

        if(contains[j][i]) size[j]--;

      dfs(dep + );

      for(int j = ; j < s; j++) //dfs切记改变了要变回来

        if(contains[j][i]) size[j]++;

    }

}

int main() {

  int T;

  scanf("%d", &T);

  while(T--) {

    init();

    best = n*n;

    dfs();

    printf("%d\n", best);

  }

  return ;

}