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