53 lines
1.1 KiB
C++
53 lines
1.1 KiB
C++
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/*
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* @Description:
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* @Version: 1.0
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* @Autor: zhuyijun
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* @Date: 2021-11-10 21:56:48
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* @LastEditTime: 2021-11-10 22:22:02
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*/
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#include <bits/stdc++.h>
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using namespace std;
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int helper(vector<int> list, int n) {
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if (n == 1 || n == 2) {
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return 1;
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}
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//判断该n是否已经计算过，如果不等于0则已经计算过 获取其值
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if (list[n] != 0) return list[n];
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list[n] = helper(list, n - 1) + helper(list, n - 2);
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return list[n];
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}
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int fbl(int n) {
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//维护一个备忘录 倍计算过的值都会被记录到里面
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vector<int> list(n + 1, 0);
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return helper(list, n);
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}
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// dp方法 1
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int fbl_dp(int n) {
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vector<int> dp(n + 1, 0);
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dp[1] = dp[2] = 1;
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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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// dp 优化
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int fbl_dp2(int n) {
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if (n == 1 || n == 2) {
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return 1;
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}
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int prev = 1, curr = 1;
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for (int i = 3; i <= n; i++) {
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int sum = prev + curr;
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prev = curr;
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curr = sum;
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}
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return curr;
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}
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int main() {
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std::cout << fbl(20) << std::endl;
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std::cout << fbl_dp(20) << std::endl;
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std::cout << fbl_dp2(20) << std::endl;
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return 0;
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}
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