68 lines
1.6 KiB
C++
68 lines
1.6 KiB
C++
// Source : https://leetcode.com/problems/happy-number/
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// Author : Hao Chen
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// Date : 2015-06-08
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/**********************************************************************************
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*
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* Write an algorithm to determine if a number is "happy".
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*
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* A happy number is a number defined by the following process: Starting with any positive integer,
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* replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1
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* (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this
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* process ends in 1 are happy numbers.
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*
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* Example: 19 is a happy number
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*
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* 1^2 + 9^2 = 82
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* 8^2 + 2^2 = 68
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* 6^2 + 8^2 = 100
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* 1^2 + 0^2 + 0^2 = 1
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*
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* Credits:Special thanks to @mithmatt and @ts 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 <map>
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using namespace std;
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int squares(int n) {
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int result = 0;
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int sq = 0;
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for (; n>0; n/=10) {
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sq = n%10;
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result += (sq * sq);
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}
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return result;
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}
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bool isHappy(int n) {
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if (n==1) return true;
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map<int, bool> m;
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m[n]=true;
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while (n!=1) {
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n = squares(n);
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//cout << n << endl;
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if (m.find(n) != m.end()){
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return false;
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}
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m[n] = true;
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}
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return true;
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}
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int main(int argc, char** argv)
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{
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int n = 2;
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if (argc > 1){
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n = atoi(argv[1]);
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}
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cout << n << (isHappy(n) ? " is " : " isn't ") << "a happy number" << endl;
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return 0;
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}
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