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# 846.Hand-of-Straights

## 题目描述

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

## 代码

### Approach #1 TreeMap to Count Slidewindow

Time: O(N * (N/W)) && Space: O(N)
class Solution {
public boolean isNStraightHand(int[] hand, int W) {
TreeMap<Integer, Integer> count = new TreeMap();
for (int card: hand) {
if (!count.containsKey(card)) {
count.put(card, 1);
} else {
count.replace(card, count.get(card) + 1);
}
}
while (count.size() > 0) {
int first = count.firstKey();
for (int card = first; card < first + W; card++) {
if (!count.containsKey(card)) return false;
int c = count.get(card);
if (c == 1) {
count.remove(card);
} else {
count.replace(card, c - 1);
}
}
}
return true;
}
}