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47 lines
1.2 KiB
47 lines
1.2 KiB
/**
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* File: climbing_stairs_backtrack.c
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* Created Time: 2023-09-22
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* Author: huawuque404 (huawuque404@163.com)
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*/
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#include "../utils/common.h"
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/* 回溯 */
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void backtrack(int *choices, int state, int n, int *res, int len) {
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// 當爬到第 n 階時，方案數量加 1
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if (state == n)
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res[0]++;
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// 走訪所有選擇
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for (int i = 0; i < len; i++) {
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int choice = choices[i];
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// 剪枝：不允許越過第 n 階
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if (state + choice > n)
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continue;
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// 嘗試：做出選擇，更新狀態
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backtrack(choices, state + choice, n, res, len);
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// 回退
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}
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}
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/* 爬樓梯：回溯 */
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int climbingStairsBacktrack(int n) {
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int choices[2] = {1, 2}; // 可選擇向上爬 1 階或 2 階
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int state = 0; // 從第 0 階開始爬
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int *res = (int *)malloc(sizeof(int));
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*res = 0; // 使用 res[0] 記錄方案數量
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int len = sizeof(choices) / sizeof(int);
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backtrack(choices, state, n, res, len);
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int result = *res;
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free(res);
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return result;
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}
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/* Driver Code */
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int main() {
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int n = 9;
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int res = climbingStairsBacktrack(n);
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printf("爬 %d 階樓梯共有 %d 種方案\n", n, res);
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return 0;
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} |