44 lines
1.0 KiB
Dart
44 lines
1.0 KiB
Dart
/**
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* File: climbing_stairs_dp.dart
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* Created Time: 2023-08-11
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* Author: liuyuxin (gvenusleo@gmail.com)
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*/
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/* Climbing stairs: Dynamic programming */
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int climbingStairsDP(int n) {
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if (n == 1 || n == 2) return n;
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// Initialize dp table, used to store subproblem solutions
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List<int> dp = List.filled(n + 1, 0);
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// Initial state: preset the smallest subproblem solution
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dp[1] = 1;
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dp[2] = 2;
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// State transition: gradually solve larger subproblems from smaller ones
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for (int i = 3; i <= n; i++) {
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dp[i] = dp[i - 1] + dp[i - 2];
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}
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return dp[n];
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}
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/* Climbing stairs: Space-optimized dynamic programming */
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int climbingStairsDPComp(int n) {
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if (n == 1 || n == 2) return n;
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int a = 1, b = 2;
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for (int i = 3; i <= n; i++) {
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int tmp = b;
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b = a + b;
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a = tmp;
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}
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return b;
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}
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/* Driver Code */
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void main() {
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int n = 9;
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int res = climbingStairsDP(n);
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print("There are $res solutions to climb $n stairs");
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res = climbingStairsDPComp(n);
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print("There are $res solutions to climb $n stairs");
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}
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