09. C Pro 深度算法求解八皇后问题

有时候真的感概,撸码并Debug一天,搞得自己头昏脑胀,结果第二天才发现,原来两行代码的执行顺序错了 -_-!

方法一、二维数组

#define N 8
int a[N][N] = { 0 };
int count = 0;

int abs(int x, int y) {
  return x >= y ? (x - y) : (y - x);
}
void dps(int x){
  if (x == N ) {
    count++;
    printf("\n方案%d:\n",count);
    for (int i = 0; i < N; i++) {
      for (int j = 0; j < N; j++) 
        printf("%d\t", a[i][j]==1?a[i][j]:0);
      printf("\n");
    }
    return;
  }

  for (int k = 0; k < N; k++) {
    if (a[x][k] == 0) {
      for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
          a[x][j] -= 1;
          a[i][k] -= 1;
          if (abs(x, i) == abs(j, k)) a[i][j] -= 1;
        }
      }
      a[x][k] = 1;
      dps(x + 1);
      for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
          a[x][j] += 1;
          a[i][k] += 1;
          if (abs(x, i) == abs(j, k)) a[i][j] += 1;
        }
      }
      a[x][k] = 0;
    }
  }

  return;
}

int main() {
  dps(0);
  getchar(); return 0;
}

 

方法二、一维数组,place函数暂时没看懂

int solution[N], j, k, count, sols;
int place(int row, int col) {
  for (j = 0; j < row; j++) {
    if (row - j == solution[row] - solution[j] || row + solution[row] == j + solution[j] || solution[j] == solution[row])
    return 0;
  }
  return 1;
}

void backtrack(int row) {
  count++;
  if (N == row) {
    sols++;
    for (k = 0; k < N; k++)
      printf("%d\t", solution[k]);
    printf("\n\n");
  }
  else {
    for (int i = 0; i < N; i++) {
      solution[row] = i;
      if (place(row, i)) backtrack(row + 1);
    }
  }
}

void queens() {
  backtrack(0);
}

int main() {
  queens();
  printf("The total solutions : %d\n", sols);
  getchar(); return 0;
}

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