452.用最少数量的箭引爆气球

class Solution {
public:
int findMinArrowShots(vector<vector>& points) {
int size = points.size();
sort(points.begin(), points.end(),
[](vector& a, vector& b) { return a[1] < b[1]; });
int ans = 0, prev = points[0][1];
for (int i = 1; i < size; i++) {
if (points[i][0] <= prev) {
ans++;
} else {
prev = points[i][1];
}
}
return size-ans;
}
};