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Split Array into Consecutive Subsequences in C++
Suppose we have an array nums that is sorted in ascending order. We have to return true if and only if we can split it into 1 or more subsequences such that each subsequence consists of consecutive integers and whose length at least 3. So if the input is like [1,2,3,3,4,4,5,5], then the output will be True, as we have two consecutive sequences. These are [1,2,3,4,5] and [3,4,5].
To solve this, we will follow these steps −
- Make a map m and store the frequency of nums into m, store size of nums into m
- cnt := n
- for i in range 0 to n – 1
- x := nums[i]
- if m[x] and m[x + 1] and m[x + 2]
- decrease m[x], m[x + 1] and m[x + 2] by 1, increase x by 3 and decrease count by 3
- while m[x] > 0 and m[x] > m[x – 1]
- decrease cnt by 1, decrease m[x] by 1 and increase x by 1
- return true if cnt is 0, otherwise false
- Let us see the following implementation to get better understanding −
Example
#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
bool isPossible(vector<int>& nums) {
unordered_map <int, int> m;
int n = nums.size();
for(int i = 0; i < n; i++){
m[nums[i]]++;
}
int cnt = n;
for(int i = 0; i < n; i++){
int x = nums[i];
if(m[x] && m[x + 1] && m[x + 2]){
m[x]--;
m[x + 1]--;
m[x + 2]--;
x += 3;
cnt -= 3;
while(m[x] > 0 && m[x] > m[x - 1]){
cnt--;
m[x]--;
x++;
}
}
}
return cnt == 0;
}
};
main(){
vector<int> v = {1,2,3,3,4,4,5,5};
Solution ob;
cout << (ob.isPossible(v));
}Input
[1,2,3,3,4,4,5,5]
Output
1
Updated on: 04-May-2020
362 Views
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