44 lines
1.4 KiB
Rust
44 lines
1.4 KiB
Rust
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pub fn plus_one(digits: Vec<i32>) -> Vec<i32> {
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// Keep track of when to carry for the next digit.
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let mut carry = false;
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// Reverse the digits so they're from least to most significant.
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let mut digits = digits.into_iter().rev();
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// Create a vector to store the incremented digits.
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let mut incremented = vec![];
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while let Some(digit) = digits.next() {
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if digit == 9 {
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// When the current digit is 9 save 0 and keep going through the digits.
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incremented.push(0);
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carry = true;
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} else {
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// When the digit isn't 9, increment it and save it, set carry to false
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// and break the loop early.
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incremented.push(digit + 1);
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carry = false;
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break;
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}
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}
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// If the last digit was a 9 we have to add an extra 1, for example:
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// [9] turns into [0] and then here we make it [0, 1].
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if carry {
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incremented.push(1);
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}
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// Then reverse both iterators so they're in the correct order and chain them.
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digits.rev().chain(incremented.into_iter().rev()).collect()
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}
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#[test]
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fn test_plus_one() {
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assert_eq!(plus_one(vec![1, 2, 3]), vec![1, 2, 4]);
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assert_eq!(plus_one(vec![4, 3, 2, 5]), vec![4, 3, 2, 6]);
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assert_eq!(plus_one(vec![9]), vec![1, 0]);
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assert_eq!(plus_one(vec![9, 9]), vec![1, 0, 0]);
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assert_eq!(plus_one(vec![7, 9, 8]), vec![7, 9, 9]);
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assert_eq!(plus_one(vec![8, 9, 9]), vec![9, 0, 0]);
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}
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