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divideTwoInt.cpp
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74 lines (64 loc) · 2.26 KB
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// Source : https://oj.leetcode.com/problems/divide-two-integers/
// Author : Hao Chen
// Date : 2014-06-20
/**********************************************************************************
*
* Divide two integers without using multiplication, division and mod operator.
*
* If it is overflow, return MAX_INT.
*
**********************************************************************************/
#include <stdio.h>
#include <string.h>
#include <iostream>
using namespace std;
#define INT_MAX 2147483647
#define INT_MIN (-INT_MAX - 1)
int divide(int dividend, int divisor) {
int sign = (float)dividend / divisor > 0 ? 1 : -1;
unsigned int dvd = dividend > 0 ? dividend : -dividend;
unsigned int dvs = divisor > 0 ? divisor : -divisor;
unsigned int bit_num[33];
unsigned int i=0;
long long d = dvs;
bit_num[i] = d;
while( d <= dvd ){
bit_num[++i] = d = d << 1;
}
i--;
unsigned int result = 0;
while(dvd >= dvs){
if (dvd >= bit_num[i]){
dvd -= bit_num[i];
result += (1<<i);
}else{
i--;
}
}
//becasue need to return `int`, so we need to check it is overflowed or not.
if ( result > INT_MAX && sign > 0 ) {
return INT_MAX;
}
return (int)result * sign;
}
int main()
{
cout << "0/2=" << divide(0, 2) << endl;
cout << "10/2=" << divide(10, 2) << endl;
cout << "10/3=" << divide(10, 3) << endl;
cout << "10/5=" << divide(10, 5) << endl;
cout << "10/7=" << divide(10, 7) << endl;
cout << "10/10=" << divide(10, 10) << endl;
cout << "10/11=" << divide(10, 11) << endl;
cout << "-1/1=" << divide(1, -1) << endl;
cout << "1/-1=" << divide(1, -1) << endl;
cout << "-1/-1=" << divide(-1, -1) << endl;
cout << "2147483647/1=" << divide(2147483647, 1) << endl;
cout << "-2147483647/1=" << divide(-2147483647, 1) << endl;
cout << "2147483647/-1=" << divide(2147483647, -1) << endl;
cout << "-2147483647/-1=" << divide(-2147483647, -1) << endl;
cout << "2147483647/2=" << divide(2147483647, 2) << endl;
cout << "2147483647/10=" << divide(2147483647, 10) << endl;
cout << "-2147483648/1=" << divide(-2147483648, 1) << endl;
cout << "-2147483648/-1=" << divide(-2147483648, -1) << endl;
}