[LeetCode 452] 用最少数量的箭引爆气球

452. 用最少数量的箭引爆气球

1.按气球前端排序

虽然过了但是很慢QAQ

class Solution {
  public:
    int findMinArrowShots(vector> &points) {
        if (points.size() == 0)
            return 0;
        sort(points.begin(), points.end(),
             [](vector x, vector y) { return x[0] < y[0]; });
        int res = 1;
        int begin = points[0][0];
        int end = points[0][1];
        for (int i = 1; i < points.size(); i++) {
            if (end >= points[i][0]) {
                begin = points[i][0];
                end = min(end, points[i][1]);
            } else {
                res++;
                begin = points[i][0];
                end = points[i][1];
            }
        }
        return res;
    }
};

2.按气球后端排序

大佬的代码简洁又快QAQ，前面sync_with_stdio那个是关同步，提高cin速度。具体可以参考 解析static auto x = []() { std::ios::sync_with_stdi..._CSDN博客

大佬的代码

static const auto io_sync_off = []()
{
    // turn off sync
    std::ios::sync_with_stdio(false);
    // untie in/out streams
    std::cin.tie(nullptr);
    return nullptr;
}();


class Solution {
public:
    int findMinArrowShots(vector>& points) {
        if (points.empty()) return 0;
        
        sort(points.begin(), points.end(), [](const auto& l, const auto& r)
             {
                return l[1] < r[1];
             });
        
        int count = 1;
        int tail = points[0][1];
        for (int i = 1; i < points.size(); i++)
        {
            if (points[i][0] <= tail) continue;
            count += 1;
            tail = points[i][1];
        }
        return count;
    }
};

一开始感觉贪心简单。。现在感觉贪心对脑子要求很高QAQ