47 lines
1.3 KiB
C
47 lines
1.3 KiB
C
/**
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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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/* Backtracking */
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void backtrack(int *choices, int state, int n, int *res, int len) {
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// When climbing to the nth step, add 1 to the number of solutions
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if (state == n)
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res[0]++;
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// Traverse all choices
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for (int i = 0; i < len; i++) {
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int choice = choices[i];
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// Pruning: do not allow climbing beyond the nth step
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if (state + choice > n)
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continue;
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// Attempt: make a choice, update the state
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backtrack(choices, state + choice, n, res, len);
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// Retract
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}
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}
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/* Climbing stairs: Backtracking */
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int climbingStairsBacktrack(int n) {
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int choices[2] = {1, 2}; // Can choose to climb up 1 step or 2 steps
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int state = 0; // Start climbing from the 0th step
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int *res = (int *)malloc(sizeof(int));
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*res = 0; // Use res[0] to record the number of solutions
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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("Climbing %d stairs has %d possible solutions\n", n, res);
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return 0;
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} |