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Strobogrammatic Number III in C++
Suppose we want to define a function to count the total strobogrammatic numbers that exist in the range of (low and high). As we know that a strobogrammatic number is a number that looks the same when rotated 180 degrees.
So, if the input is like low = "50", high = "100", then the output will be 3 as there are three results, 69, 88, and 96.
To solve this, we will follow these steps −
Define a function findStrobogrammatic(), this will take n,
Define an array ret
if n & 1 is non-zero, then −
insert "0" at the end of ret
insert "1" at the end of ret
insert "8" at the end of ret
Otherwise
insert blank string at the end of ret
for n > 1, update n := n - 2, do −
Define an array temp
for initialize i := 0, when i < size of ret, update (increase i by 1), do −
s := ret[i]
if n > 3, then −
insert "0" + s + "0" at the end of temp
insert "1" + s + "1" at the end of temp
insert "8" + s + "8" at the end of temp
insert "6" + s + "9" at the end of temp
insert "9" + s + "6" at the end of temp
ret := temp
return ret
From the main method, do the following −
ret := 0
Define an array v
for initialize i := size of low, when i <= size of high, update (increase i by 1), do −
v := findStrobogrammatic(i)
for initialize j := 0, when j < size of v, update (increase j by 1), do −
ret := ret + (1 when length of v[j] > length of low AND length of high > length of v[j])
return ret
Example
Let us see the following implementation to get better understanding −
#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
vector<string> findStrobogrammatic(int n) {
vector<string> ret;
if (n & 1) {
ret.push_back("0");
ret.push_back("1");
ret.push_back("8");
}
else {
ret.push_back("");
}
for (; n > 1; n -= 2) {
vector<string> temp;
for (int i = 0; i < ret.size(); i++) {
string s = ret[i];
if (n > 3) {
temp.push_back("0" + s + "0");
}
temp.push_back("1" + s + "1");
temp.push_back("8" + s + "8");
temp.push_back("6" + s + "9");
temp.push_back("9" + s + "6");
}
ret = temp;
}
return ret;
}
bool compare(string a, string b){
return a.size() == b.size() ? a >= b : a.size() > b.size();
}
int strobogrammaticInRange(string low, string high) {
int ret = 0;
vector<string> v;
for (int i = low.size(); i <= high.size(); i++) {
v = findStrobogrammatic(i);
for (int j = 0; j < v.size(); j++) {
ret += compare(v[j], low) && compare(high, v[j]);
}
}
return ret;
}
};
main(){
Solution ob;
cout <<(ob.strobogrammaticInRange("50", "100"));
}Input
"50","100"
Output
3
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