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reverseInteger.cpp
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79 lines (74 loc) · 2.29 KB
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// Source : https://oj.leetcode.com/problems/reverse-integer/
// Author : Hao Chen
// Date : 2014-06-18
/**********************************************************************************
*
* Reverse digits of an integer.
*
* Example1: x = 123, return 321
* Example2: x = -123, return -321
*
*
* Have you thought about this?
*
* Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!
*
* > If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.
*
* > Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer,
* then the reverse of 1000000003 overflows. How should you handle such cases?
*
* > Throw an exception? Good, but what if throwing an exception is not an option?
* You would then have to re-design the function (ie, add an extra parameter).
*
*
**********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
//Why need the INT_MIN be defined like that?
//Please take a look:
// http://stackoverflow.com/questions/14695118/2147483648-0-returns-true-in-c
#define INT_MAX 2147483647
#define INT_MIN (-INT_MAX - 1)
int reverse(int x) {
int y=0;
int n;
while( x != 0){
n = x%10;
//Checking the over/underflow.
//Actually, it should be y>(INT_MAX-n)/10, but n/10 is 0, so omit it.
if (y > INT_MAX/10 || y < INT_MIN/10){
return 0;
}
y = y*10 + n;
x /= 10;
}
return y;
}
#define TEST(n, e) printf("%12d => %-12d %s!\n", n, reverse(n), e == reverse(n)?"passed":"failed")
int main(int argc, char**argv)
{
//basic cases
TEST( 123, 321);
TEST( -123, -321);
TEST( -100, -1);
TEST( 1002, 2001);
//big integer
TEST( 1463847412, 2147483641);
TEST(-2147447412, -2147447412);
TEST( 2147447412, 2147447412);
//overflow
TEST( 1000000003, 0);
TEST( 2147483647, 0);
TEST(-2147483648, 0);
//customized cases
if (argc<2){
return 0;
}
printf("\n");
for (int i=1; i<argc; i++) {
int n = atoi(argv[i]);
printf("%12d => %-12d %s!\n", n, reverse(n), reverse(reverse(n))==n ? "passed":"failed");
}
return 0;
}