Problem

题目大意：给你一些牌，问你能否分组，要求每组w张连续的牌。

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:

Solution: Greedy

Time complexity: O(nlogn)

Space complexity: O(n)

// Author: Huahua

// Running time: 65 ms

class Solution {

public:

bool isNStraightHand(vector<int>& hand, int W) {

map<int, int> counts;

for (int h : hand) ++counts[h];

while (!counts.empty()) {

auto it = counts.begin();

int start = it->first;

for (int j = 0; j < W; ++j) {

if (it == counts.end()

|| it->first != start + j) return false;

auto prev = it++;

if (--(prev->second) == 0)

counts.erase(prev);

}

return true;

}

};

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