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24 lines
554 B
24 lines
554 B
#include <bits/stdc++.h>
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using namespace std;
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int n;
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int res;
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void dfs(int u, string t) {
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if (u == 2 * n + 1) {
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if (t.size() == 0) res++;
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return;
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}
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//当前填充{
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dfs(u + 1, t + "{");
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if (t.back() == '{') //如果t的最后一个字符是 {
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t.pop_back(), dfs(u + 1, t); //当前填充},就会对掉一对{}
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// t.substr(0,t.size()-1) 去掉尾巴
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else
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dfs(u + 1, t + "}");
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}
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int main() {
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cin >> n;
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dfs(1, "");
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cout << res << endl;
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return 0;
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} |