编译优化

#pragma GCC optimize(0) ->

#pragma GCC optimize(3) ->

#pragma GCC optimize(3, "inline")

5.2s -> 1.8s -> 1.0s

吸氧大法好 QAQ 。

#pragma GCC optimize(3, "inline")
#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;

u64 f(int u) {
    if (u == 1)
        return 1ULL;
    else if (u == 2)
        return 1ULL;
    else {
        return f(u - 2) + f(u - 1);
    }
}

int main() {
    std::cout << f(45) << '\n' << ((double)clock() / CLOCKS_PER_SEC) << "s\n";
    return 0;
}