[LeetCode]29. Divide Two Integers

Problem Description

[]https://leetcode.com/problems/divide-two-integers/]

Divide two integers without using multiplication, division and mod operator.

If it is overflow, return MAX_INT.

思路

没啥好说的，最讨厌做有关int范围的题了。。边界好多。。。

Code

package q029;

public class Solution {

public int divide(int dividend, int divisor) {
long mydividend = dividend;
long mydivisor = divisor;
if (mydivisor == 0)
return Integer.MAX_VALUE;
int tmp = 1;
if (mydividend < 0) {
mydividend = -mydividend;
tmp = -tmp;
}
if (mydivisor < 0) {
mydivisor = -mydivisor;
tmp = -tmp;
}
if (mydividend < mydivisor)
return 0;
long[] bits = new long[31];
bits[0] = mydivisor;
int i;
for (i = 1; i <= 30; i++) {
bits[i] = bits[i - 1] + bits[i - 1];
if (bits[i] > mydividend)
break;
}
i--;
long ans = 0;
while (mydividend >= mydivisor) {
mydividend -= bits[i];
ans += 1 << i;
while (i > 0 && bits[i] > mydividend)
i--;
}
ans = ans * tmp;
if (ans > Integer.MAX_VALUE)
return Integer.MAX_VALUE;
return (int) ans;
}

}