LeetCode Q246: Strobogrammatric Number

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

For example, the numbers "69", "88", and "818" are all strobogrammatic.

Solution:

The string should be sort of like palindrome.

	class Solution {
	public:
	bool isStrobogrammatic(string num) {
	for(int i=0; i<num.size(); i++)
	if(num[i]!='0'&&num[i]!='1'&&num[i]!='6'&&num[i]!='8'&&num[i]!='9')
	return false;
	string tmp = num;
	reverse(tmp.begin(), tmp.end());
	for(int i=0; i<num.size(); i++){
	if(tmp[i]=='6'){
	tmp[i]='9';
	continue;
	}
	if(tmp[i]=='9'){
	tmp[i]='6';
	continue;
	}
	}
	for(int i=0; i<num.size(); i++){
	if(num[i]!=tmp[i])
	return false;
	}
	return true;
	}
	};

view raw Q246StrobogrammaticNumber.cpp hosted with ❤ by GitHub

Round 2 solution:

	class Solution {
	public:
	bool isStrobogrammatic(string num) {
	if(num.empty())
	return true;
	int p0=0, p1=num.size()-1;
	while(p0<=p1){
	if(num[p0]!='0'&&num[p0]!='1'&&num[p0]!='6'&&num[p0]!='8'&&num[p0]!='9' &&
	num[p1]!='0'&&num[p1]!='1'&&num[p1]!='6'&&num[p1]!='8'&&num[p1]!='9')
	return false;
	if((num[p0]=='6'&&num[p1]!='9') || (num[p0]=='9'&&num[p1]!='6'))
	return false;
	if(num[p0]!='6'&&num[p0]!='9'&&num[p0]!=num[p1])
	return false;
	p0++;
	p1--;
	}
	return true;
	}
	};

view raw Q246Rnd2.cpp hosted with ❤ by GitHub