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krahets
2023-10-18 02:16:55 +08:00
parent 64c5d13051
commit d2ba55fcd6
22 changed files with 374 additions and 436 deletions
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31
docs/chapter_backtracking/n_queens_problem.md
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@@ -601,25 +601,17 @@ comments: true
=== "C"
```c title="n_queens.c"
/* 放置结果 */
struct result {
char ***data;
int size;
};
typedef struct result Result;
/* 回溯算法：N 皇后 */
void backtrack(int row, int n, char state[MAX_N][MAX_N], Result *res,
bool cols[MAX_N], bool diags1[2 * MAX_N - 1], bool diags2[2 * MAX_N - 1]) {
void backtrack(int row, int n, char state[MAX_N][MAX_N], char ***res, int *resSize, bool cols[MAX_N],
bool diags1[2 * MAX_N - 1], bool diags2[2 * MAX_N - 1]) {
// 当放置完所有行时，记录解
if (row == n) {
res->data[res->size] = (char **)malloc(sizeof(char *) * n);
res[*resSize] = (char **)malloc(sizeof(char *) * n);
for (int i = 0; i < n; ++i) {
res->data[res->size][i] = (char *)malloc(sizeof(char) * (n + 1));
strcpy(res->data[res->size][i], state[i]);
res[*resSize][i] = (char *)malloc(sizeof(char) * (n + 1));
strcpy(res[*resSize][i], state[i]);
}
res->size++;
(*resSize)++;
return;
}
// 遍历所有列
@@ -633,7 +625,7 @@ comments: true
state[row][col] = 'Q';
cols[col] = diags1[diag1] = diags2[diag2] = true;
// 放置下一行
backtrack(row + 1, n, state, res, cols, diags1, diags2);
backtrack(row + 1, n, state, res, resSize, cols, diags1, diags2);
// 回退：将该格子恢复为空位
state[row][col] = '#';
cols[col] = diags1[diag1] = diags2[diag2] = false;
@@ -642,7 +634,7 @@ comments: true
}
/* 求解 N 皇后 */
Result *nQueens(int n) {
char ***nQueens(int n, int *returnSize) {
char state[MAX_N][MAX_N];
// 初始化 n*n 大小的棋盘，其中 'Q' 代表皇后，'#' 代表空位
for (int i = 0; i < n; ++i) {
@@ -655,10 +647,9 @@ comments: true
bool diags1[2 * MAX_N - 1] = {false}; // 记录主对角线是否有皇后
bool diags2[2 * MAX_N - 1] = {false}; // 记录副对角线是否有皇后
Result *res = malloc(sizeof(Result));
res->data = (char ***)malloc(sizeof(char **) * MAX_RES);
res->size = 0;
backtrack(0, n, state, res, cols, diags1, diags2);
char ***res = (char ***)malloc(sizeof(char **) * MAX_RES);
*returnSize = 0;
backtrack(0, n, state, res, returnSize, cols, diags1, diags2);
return res;
}
```