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Longest Happy String in C++
Suppose there is a string. That string is called happy if it does not have any of the strings like 'aaa', 'bbb' or 'ccc' as a substring. If we have three integers like a, b and c, then return any string s, which satisfies the following conditions −
s is happy and longest possible.
s contains at most an occurrence of the letter 'a', at most b occurrences of the letter 'b' and at most c occurrences of the letter 'c'.
s will only contain 'a', 'b' and 'c' letters.
If there is no such string, then return an empty string.
So, if the input is like a = 1, b = 1, c = 7, then the output will be "ccaccbcc"
To solve this, we will follow these steps −
Define one data structure where character a, inx and cnt is present
Define one priority queue pq, this will prioritize using cnt value of data
if a is non-zero, then −
insert new Data('a', a, 0) into pq
if b is non-zero, then −
insert new Data('b', b, 0) into pq
if c is non-zero, then −
insert new Data('c', c, 0) into pq
idx := 1
ret := blank string
while true is non-zero, do −
temp := top element of pq
delete element from pq
if size of ret is not 0 and last element of ret is same as temp.a, then −
if pq is empty, then −
Come out from the loop
x := temp
temp := top element of pq
delete element from pq
insert x into pq
val := 0
if not pq is empty and cnt of temp - cnt of first element of pq < 2, then −
val := 1
Otherwise
val := minimum of cnt of temp and 2
ret := ret concatenate val from index of temp.a in val to end
temp.cnt := temp.cnt - val
if pq is empty, then −
Come out from the loop
temp.idx := idx
if temp.cnt > 0, then −
insert temp into pq
(increase idx by 1)
return ret
Example
Let us see the following implementation to get a better understanding −
#include <bits/stdc++.h>
using namespace std;
struct Data{
char a;
int cnt;
int idx ;
Data(char c, int x, int k){
a = c;
cnt = x;
idx = k;
}
};
struct Cmp{
bool operator()(Data& a, Data& b) {
return !(a.cnt>b.cnt);
}
};
class Solution {
public:
string longestDiverseString(int a, int b, int c) {
priority_queue<Data, vector<Data>, Cmp> pq;
if (a)
pq.push(Data('a', a, 0));
if (b)
pq.push(Data('b', b, 0));
if (c)
pq.push(Data('c', c, 0));
int idx = 1;
string ret = "";
while (true) {
Data temp = pq.top();
pq.pop();
if (ret.size() && ret.back() == temp.a) {
if (pq.empty())
break;
Data x = temp;
temp = pq.top();
pq.pop();
pq.push(x);
}
int val = 0;
if (!pq.empty() && temp.cnt - pq.top().cnt < 2) {
val = 1;
}
else
val = min(temp.cnt, 2);
ret += string(val, temp.a);
temp.cnt -= val;
if (pq.empty())
break;
temp.idx = idx;
if (temp.cnt > 0)
pq.push(temp);
idx++;
}
return ret;
}
};
main(){
Solution ob;
cout << (ob.longestDiverseString(1,1,7));
}Input
1,1,7
Output
ccbccacc
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