129 lines
3.2 KiB
C++
129 lines
3.2 KiB
C++
// Source : https://oj.leetcode.com/problems/fraction-to-recurring-decimal/
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// Author : Hao Chen
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// Date : 2014-12-16
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/**********************************************************************************
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*
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* Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.
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*
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* If the fractional part is repeating, enclose the repeating part in parentheses.
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*
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* For example,
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*
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* Given numerator = 1, denominator = 2, return "0.5".
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* Given numerator = 2, denominator = 1, return "2".
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* Given numerator = 2, denominator = 3, return "0.(6)".
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*
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* Credits:Special thanks to @Shangrila for adding this problem and creating all test cases.
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*
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**********************************************************************************/
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#include <stdlib.h>
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#include <iostream>
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#include <sstream>
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#include <string>
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#include <map>
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using namespace std;
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/*
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* Be careful the following cases:
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*
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* > 0/2
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* > 1/0
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* > 1/3
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* > 2/4
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* > 100/2
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* > 100/3
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* > 1/-4
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* > -1/4
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* > -1/-4
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* > 25/99 = 0.25252525....
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* > 1/7 = 0.142857142857...
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* > 1/17 = 0.(0588235294117647)
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*/
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string fractionToDecimal(int numerator, int denominator) {
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string result;
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//deal with the `ZERO` cases
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if (denominator == 0){ return result; }
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if (numerator == 0) { return "0"; }
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//using long long type make sure there has no integer overflow
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long long n = numerator;
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long long d = denominator;
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//deal with negtive cases
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bool sign = ((float)numerator/denominator >= 0);
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if ( n < 0 ){ n = -n; }
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if ( d < 0 ){ d = -d; }
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if (sign == false){
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result.push_back('-');
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}
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long long remainder = n % d;
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long long division = n / d;
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ostringstream oss;
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oss << division;
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result += oss.str();
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if (remainder == 0){
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return result;
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}
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//remainder has value, the result is a float
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result.push_back('.');
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//using a map to record all of reminders and their position.
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//if the reminder appeared before, which means the repeated loop begin,
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//then, get the place from map to insert "(".
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//(In C++11, it's better to use unordered_map )
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map<long long, int> rec;
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for (int pos=result.size(); remainder!=0; pos++, remainder=(remainder*10)%d ) {
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if (rec.find(remainder) != rec.end()) {
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result.insert(result.begin()+rec[remainder], '(');
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result.push_back(')');
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return result;
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}
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rec[remainder] = pos;
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result.push_back((remainder*10)/d + '0');
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}
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return result;
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}
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void test(int num, int deno)
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{
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cout << "numerator: " << num << "\tdenominator: " << deno << "\tresult: " << fractionToDecimal(num, deno) << endl;
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}
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int main(int argc, char** argv)
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{
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test(1, 2);
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test(10, 2);
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test(100, 2);
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test(1, 3);
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test(100, 3);
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test(1, 6);
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test(100, 6);
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test(-1, 4);
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test(1, -3);
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test(-1, -6);
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test(25, 99);
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test(1, 7);
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test(10, 7);
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test(100, 7);
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test(1, 17);
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test(1, 1024);
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test( -2147483648, -1999);
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test(-1, -2147483648);
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if (argc > 2) {
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int num = atoi(argv[1]);
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int deno = atoi(argv[2]);
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test(num, deno);
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}
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return 0;
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}
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