##### Welcome to Subscribe On Youtube

Formatted question description: https://leetcode.ca/all/846.html

# 846. Hand of Straights (Medium)

Alice has a hand of cards, given as an array of integers.

Now she wants to rearrange the cards into groups so that each group is size W, and consists of W consecutive cards.

Return true if and only if she can.

Example 1:

Input: hand = [1,2,3,6,2,3,4,7,8], W = 3
Output: true
Explanation: Alice's hand can be rearranged as [1,2,3],[2,3,4],[6,7,8].

Example 2:

Input: hand = [1,2,3,4,5], W = 4
Output: false
Explanation: Alice's hand can't be rearranged into groups of 4.


Constraints:

• 1 <= hand.length <= 10000
• 0 <= hand[i] <= 10^9
• 1 <= W <= hand.length

Note: This question is the same as 1296: https://leetcode.com/problems/divide-array-in-sets-of-k-consecutive-numbers/

Related Topics:
Ordered Map

## Solution 1. Multiset

// OJ: https://leetcode.com/problems/hand-of-straights/
// Time: O(NlogN)
// Space: O(N)
class Solution {
public:
bool isNStraightHand(vector<int>& A, int W) {
multiset<int> s(begin(A), end(A));
while (s.size()) {
int n = *s.begin();
s.erase(s.begin());
for (int i = 1; i < W; ++i) {
auto it = s.find(n + i);
if (it == s.end()) return false;
s.erase(it);
}
}
return true;
}
};


## Solution 2. Map

// OJ: https://leetcode.com/problems/hand-of-straights/
// Time: O(NlogN)
// Space: O(N)
class Solution {
public:
bool isNStraightHand(vector<int>& A, int W) {
map<int, int> m;
for (int n : A) m[n]++;
while (m.size()) {
int n = m.begin()->first;
if (--m[n] == 0) m.erase(n);
for (int i = 1; i < W; ++i) {
if (m.count(n + i) == 0) return false;
if (--m[n + i] == 0) m.erase(n + i);
}
}
return true;
}
};


One optimization is that we can delete multiple group at the same time.

// OJ: https://leetcode.com/problems/hand-of-straights/
// Time: O(NlogN)
// Space: O(N)
class Solution {
public:
bool isNStraightHand(vector<int>& A, int W) {
map<int, int> m;
for (int n : A) m[n]++;
while (m.size()) {
int n = m.begin()->first, cnt = m.begin()->second;
m.erase(n);
for (int i = 1; i < W; ++i) {
if (m[n + i] < cnt) return false;
if ((m[n + i] -= cnt) == 0) m.erase(n + i);
}
}
return true;
}
};

• class Solution {
public boolean isNStraightHand(int[] hand, int W) {
if (hand == null || hand.length == 0)
return false;
int length = hand.length;
if (length % W != 0)
return false;
TreeMap<Integer, Integer> map = new TreeMap<Integer, Integer>();
for (int num : hand) {
int count = map.getOrDefault(num, 0) + 1;
map.put(num, count);
}
while (map.size() > 0) {
int start = map.firstKey();
int end = start + W - 1;
for (int i = start; i <= end; i++) {
int count = map.getOrDefault(i, 0);
if (count == 0)
return false;
count--;
if (count == 0)
map.remove(i);
else
map.put(i, count);
}
}
return true;
}
}

############

class Solution {
public boolean isNStraightHand(int[] hand, int groupSize) {
Map<Integer, Integer> cnt = new HashMap<>();
for (int v : hand) {
cnt.put(v, cnt.getOrDefault(v, 0) + 1);
}
Arrays.sort(hand);
for (int v : hand) {
if (cnt.containsKey(v)) {
for (int x = v; x < v + groupSize; ++x) {
if (!cnt.containsKey(x)) {
return false;
}
cnt.put(x, cnt.get(x) - 1);
if (cnt.get(x) == 0) {
cnt.remove(x);
}
}
}
}
return true;
}
}

• // OJ: https://leetcode.com/problems/hand-of-straights/
// Time: O(NlogN)
// Space: O(N)
class Solution {
public:
bool isNStraightHand(vector<int>& A, int W) {
multiset<int> s(begin(A), end(A));
while (s.size()) {
int n = *s.begin();
s.erase(s.begin());
for (int i = 1; i < W; ++i) {
auto it = s.find(n + i);
if (it == s.end()) return false;
s.erase(it);
}
}
return true;
}
};

• class Solution:
def isNStraightHand(self, hand: List[int], groupSize: int) -> bool:
cnt = Counter(hand)
for v in sorted(hand):
if cnt[v]:
for x in range(v, v + groupSize):
if cnt[x] == 0:
return False
cnt[x] -= 1
if cnt[x] == 0:
cnt.pop(x)
return True

############

class Solution(object):
def isNStraightHand(self, hand, W):
"""
:type hand: List[int]
:type W: int
:rtype: bool
"""
cards = collections.Counter(hand)
while cards:
start = min(cards.keys())
start_val = cards[start]
for card in range(start, start + W):
if card not in cards:
return False
cards[card] -= start_val
if cards[card] == 0:
cards.pop(card)
elif cards[card] < 0:
return False
return not cards

• func isNStraightHand(hand []int, groupSize int) bool {
cnt := map[int]int{}
for _, v := range hand {
cnt[v]++
}
sort.Ints(hand)
for _, v := range hand {
if _, ok := cnt[v]; ok {
for x := v; x < v+groupSize; x++ {
if _, ok := cnt[x]; !ok {
return false
}
cnt[x]--
if cnt[x] == 0 {
delete(cnt, x)
}
}
}
}
return true
}