80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
// Source : https://oj.leetcode.com/problems/reverse-integer/
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// Author : Hao Chen
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// Date : 2014-06-18
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/**********************************************************************************
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*
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* Reverse digits of an integer.
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*
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* Example1: x = 123, return 321
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* Example2: x = -123, return -321
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*
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*
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* Have you thought about this?
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*
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* Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!
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*
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* > If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.
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*
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* > Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer,
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* then the reverse of 1000000003 overflows. How should you handle such cases?
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*
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* > Throw an exception? Good, but what if throwing an exception is not an option?
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* You would then have to re-design the function (ie, add an extra parameter).
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*
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*
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**********************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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//Why need the INT_MIN be defined like that?
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//Please take a look:
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// http://stackoverflow.com/questions/14695118/2147483648-0-returns-true-in-c
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#define INT_MAX 2147483647
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#define INT_MIN (-INT_MAX - 1)
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int reverse(int x) {
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int y=0;
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int n;
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while( x != 0){
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n = x%10;
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//Checking the over/underflow.
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//Actually, it should be y>(INT_MAX-n)/10, but n/10 is 0, so omit it.
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if (y > INT_MAX/10 || y < INT_MIN/10){
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return 0;
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}
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y = y*10 + n;
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x /= 10;
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}
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return y;
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}
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#define TEST(n, e) printf("%12d => %-12d %s!\n", n, reverse(n), e == reverse(n)?"passed":"failed")
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int main(int argc, char**argv)
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{
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//basic cases
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TEST( 123, 321);
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TEST( -123, -321);
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TEST( -100, -1);
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TEST( 1002, 2001);
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//big integer
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TEST( 1463847412, 2147483641);
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TEST(-2147447412, -2147447412);
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TEST( 2147447412, 2147447412);
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//overflow
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TEST( 1000000003, 0);
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TEST( 2147483647, 0);
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TEST(-2147483648, 0);
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//customized cases
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if (argc<2){
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return 0;
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}
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printf("\n");
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for (int i=1; i<argc; i++) {
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int n = atoi(argv[i]);
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printf("%12d => %-12d %s!\n", n, reverse(n), reverse(reverse(n))==n ? "passed":"failed");
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}
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return 0;
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}
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