[算法练习]Reverse Integer

题目说明：

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return –321

程序代码：

#include <gtest/gtest.h>
using namespace std;

int reverse2(int x) 
{
    int result[20] = {0};
    int resultIdx = 0;
    int sign = 1;
    long long val = x;
    if (val < 0)
    {
        sign = -1;
        val = -val;
    }

    while (val)
    {
        result[resultIdx++] = val % 10;
        val /= 10;
    }

    long long newResult = 0;
    long long base = 1;
    for (int i = resultIdx-1; i >= 0; i--)
    {
        newResult += result[i] * base;
        base *= 10;
    }

    if (newResult > 0x7FFFFFFF)
    {
        newResult = 0;
    }

    newResult *= sign;

    return (int)newResult;
}

int reverse(int x) 
{
    int result[20] = {0};
    int resultIdx = 0;

    while (x)
    {
        result[resultIdx++] = x % 10;
        x /= 10;
    }

    long long newResult = 0;
    long long base = 1;
    for (int i = resultIdx-1; i >= 0; i--)
    {
        newResult += result[i] * base;
        base *= 10;
    }

    if ((newResult > 0x7FFFFFFF) || (newResult < -0x7FFFFFFF))
    {
        newResult = 0;
    }

    return (int)newResult;
}

TEST(Pratices, tReverse)
{
    // 123 -> 321
    ASSERT_EQ(reverse(123),321);
    // -123 -> -321
    ASSERT_EQ(reverse(-123),-321);
    // 0 -> 0
    ASSERT_EQ(reverse(0),0);
    // -0 -> 0
    ASSERT_EQ(reverse(-0),0);
    // 0x1FFFFFFF -> 0x7FFFFFFF
    ASSERT_EQ(reverse(-2147483648),0);
    // -0x1FFFFFFF -> -0x7FFFFFFF
    //ASSERT_EQ(reverse(-0x1FFFFFFF),-0x7FFFFFFF);
}