24 lines
559 B
Rust
24 lines
559 B
Rust
fn persistence(num: u64) -> u64 {
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match num {
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0..=9 => 0,
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_ => {
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let res = num
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.to_string()
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.chars()
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.map(|c| c.to_digit(10).unwrap() as u64)
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.product();
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1 + persistence(res)
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}
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}
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}
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#[cfg(test)]
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mod tests {
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#[test]
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fn sample_tests() {
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assert_eq!(super::persistence(39), 3);
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assert_eq!(super::persistence(4), 0);
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assert_eq!(super::persistence(25), 2);
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assert_eq!(super::persistence(999), 4);
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}
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}
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