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40 lines
761 B
40 lines
761 B
#include <bits/stdc++.h>
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// 超棒的讲解
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// https://www.bilibili.com/video/BV1nE411A7ST?from=search&seid=2618099886973795159
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using namespace std;
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/**
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如果n=1 1
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如果n=2 2
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如果n=3 5
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如果n=4 14
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如果n=5 42
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如果n=6 132
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如果n=7 429
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如果n=8 1430
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如果n=9 4862
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如果n=10 16796
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如果n=11 58786
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如果n=12 208012
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如果n=13 742900
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如果n=14 2674440
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如果n=15 9694845
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如果n=16 35357670
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如果n=17 129644790
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如果n=18 477638700
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卡特兰数！！！
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*/
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int catalan(int n) {
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if (n == 0 || n == 1) return 1;
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int res = 0;
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for (int i = 1; i <= n; i++) res += catalan(i - 1) * catalan(n - i);
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return res;
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}
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int main() {
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int n;
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cin >> n;
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cout << catalan(n) << endl;
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return 0;
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} |