56 lines
1.2 KiB
Ruby
56 lines
1.2 KiB
Ruby
def my_atoi(s)
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res = 0
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sign = 1
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sign_was_scanned = false
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digit_was_scanned = false
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i32_min = -2_147_483_648
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i32_max = 2_147_483_647
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s.each_char do |c|
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if c >= '0' && c <= '9'
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digit_was_scanned = true
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conv = c.ord - '0'.ord
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# Add new digit
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res = res * 10 + conv * sign
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# Test overflow
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return i32_max if sign > 0 && res > i32_max
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return i32_min if sign < 0 && res < i32_min
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# First '-'
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elsif c == '-' && sign_was_scanned == false && digit_was_scanned == false
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sign_was_scanned = true
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sign *= -1
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# First '+'
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elsif c == '+' && sign_was_scanned == false && digit_was_scanned == false
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sign_was_scanned = true
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# Repeated '-' or '-' after number
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elsif c == '-'
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return res
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# Repeated '+' or '+' after number
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elsif c == '+'
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return res
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# Letters before number
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elsif c != '+' && c != ' ' && digit_was_scanned == false
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return 0
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# Space after sign
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elsif c == ' ' && sign_was_scanned
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return res
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# Letters after number
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elsif digit_was_scanned == true
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return res
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end
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end
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res
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end
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