22 lines
711 B
Rust
22 lines
711 B
Rust
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fn main() {
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let mut buf = String::new();
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std::io::stdin().read_line(&mut buf).ok();
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let n: usize = buf.trim().parse::<usize>().unwrap();
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buf.clear();
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std::io::stdin().read_line(&mut buf).ok();
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let a: Vec<i64> = buf.trim().split(' ').map(|x|x.parse::<i64>().unwrap()).collect::<Vec<i64>>();
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let mut pa = vec![0;n+1];
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let mut sa = vec![0;n+1];
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pa[0] = 0 - n as i64 - 1;
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for i in 1..=n {
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pa[i] = pa[i-1].max(a[i-1] - i as i64 - 1);
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}
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for i in (0..n).rev() {
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sa[i] = sa[i+1].max(a[i] + i as i64);
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}
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let mut res = i64::MAX;
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for i in 0..n {
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res = res.min(a[i].max((pa[i] + n as i64 + 1).max(sa[i+1])));
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}
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println!("{res}");
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}
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