leetcode/algorithms/cpp/divideTwoInt/divideTwoInt.cpp at master · nadbp/leetcode · GitHub

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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>
usingnamespacestd;

#defineINT_MAX2147483647
#defineINT_MIN (-INT_MAX - 1)

intdivide(int dividend, int divisor) {

int sign = (float)dividend / divisor > 0 ? 1 : -1;
unsignedint dvd = dividend > 0 ? dividend : -dividend;
unsignedint dvs = divisor > 0 ? divisor : -divisor;

unsignedint bit_num[33];
unsignedint i=0;
longlong d = dvs;
 bit_num[i] = d;
while( d <= dvd ){
 bit_num[++i] = d = d << 1;
 }
 i--;

unsignedint 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 ) {
returnINT_MAX;
 }
return (int)result * sign;
}


intmain()
{
 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;
}