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102 lines
2.9 KiB
102 lines
2.9 KiB
/**
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* File: preorder_traversal_iii_template.c
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* Created Time: 2023-06-04
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* Author: Gonglja (glj0@outlook.com)
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*/
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#include "../utils/common.h"
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/* 判断当前状态是否为解 */
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bool isSolution(vector *state) {
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return state->size != 0 && ((TreeNode *)(state->data[state->size - 1]))->val == 7;
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}
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/* 记录解 */
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void recordSolution(vector *state, vector *res) {
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vector *newPath = newVector();
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for (int i = 0; i < state->size; i++) {
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vectorPushback(newPath, state->data[i], sizeof(int));
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}
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vectorPushback(res, newPath, sizeof(vector));
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}
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/* 判断在当前状态下，该选择是否合法 */
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bool isValid(vector *state, TreeNode *choice) {
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return choice != NULL && choice->val != 3;
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}
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/* 更新状态 */
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void makeChoice(vector *state, TreeNode *choice) {
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vectorPushback(state, choice, sizeof(TreeNode));
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}
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/* 恢复状态 */
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void undoChoice(vector *state, TreeNode *choice) {
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vectorPopback(state);
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}
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/* 前序遍历：例题三 */
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void backtrack(vector *state, vector *choices, vector *res) {
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// 检查是否为解
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if (isSolution(state)) {
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// 记录解
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recordSolution(state, res);
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return;
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}
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// 遍历所有选择
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for (int i = 0; i < choices->size; i++) {
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TreeNode *choice = choices->data[i];
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// 剪枝：检查选择是否合法
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if (isValid(state, choice)) {
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// 尝试：做出选择，更新状态
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makeChoice(state, choice);
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// 进行下一轮选择
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vector *nextChoices = newVector();
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vectorPushback(nextChoices, choice->left, sizeof(TreeNode));
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vectorPushback(nextChoices, choice->right, sizeof(TreeNode));
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backtrack(state, nextChoices, res);
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// 回退：撤销选择，恢复到之前的状态
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undoChoice(state, choice);
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}
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}
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}
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// 打印向量中的元素
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void printFunc(vector *v, void *p) {
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TreeNode *node = p;
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printf("%d ", node->val);
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}
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/* Driver Code */
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int main() {
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int arr[] = {1, 7, 3, 4, 5, 6, 7};
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int n = sizeof(arr) / sizeof(arr[0]);
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TreeNode *root = arrToTree(arr, n);
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printf("\r\n初始化二叉树\r\n");
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printTree(root);
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// 回溯算法
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vector *state = newVector();
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vector *choices = newVector();
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vector *res = newVector();
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vectorPushback(choices, root, sizeof(TreeNode));
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backtrack(state, choices, res);
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printf("输出所有根节点到节点 7 的路径，要求路径中不包含值为 3 的节点:\n");
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for (int i = 0; i < res->size; i++) {
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vector *path = res->data[i];
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vector *vals = newVector();
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for (int j = 0; j < path->size; j++) {
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TreeNode *node = path->data[j];
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vectorPushback(vals, &node->val, sizeof(int));
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}
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printVector(vals, printFunc);
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}
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// 释放内存
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delVector(state);
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delVector(choices);
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delVector(res);
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return 0;
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}
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