I was practicing an old problem [757G](https://codeforces.net/contest/757/problem/G) and I met a huge speed difference among different c++ standard. ↵
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I [received TLE](https://codeforces.net/contest/757/submission/208910787) (> 5000ms) when submitting with c++17 (64, win). But the exact same code do run fast (< 800ms) in the corresponding testcase when submitting with [c++17] (https://codeforces.net/contest/757/submission/208910712) or [c++20 (64, win)] (https://codeforces.net/contest/757/submission/208910479). ↵
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I'm wondering why this could happen. I will be graceful if kindly everybody could point out the reason.
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I [received TLE](https://codeforces.net/contest/757/submission/208910787) (> 5000ms) when submitting with c++17 (64, win). But the exact same code do run fast (< 800ms) in the corresponding testcase when submitting with [c++17] (https://codeforces.net/contest/757/submission/208910712) or [c++20 (64, win)] (https://codeforces.net/contest/757/submission/208910479). ↵
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I'm wondering why this could happen. I will be graceful if kindly everybody could point out the reason.
