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;
}
};


Java

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;
}
}