LazySegmentTree.py 文件源码

def query(self, idx, l, r, a, b): #query(1, 1, N, a, b) for query max of [a,b]
        if self.flag[idx] == True:
            self.st[idx] = self.lazy[idx]
            self.flag[idx] = False
            if l != r:
                self.lazy[self.left(idx)] = self.lazy[idx]
                self.lazy[self.right(idx)] = self.lazy[idx]
                self.flag[self.left(idx)] = True
                self.flag[self.right(idx)] = True
        if r < a or l > b:
            return -math.inf
        if l >= a and r <= b:
            return self.st[idx]
        mid = (l+r)//2
        q1 = self.query(self.left(idx),l,mid,a,b)
        q2 = self.query(self.right(idx),mid+1,r,a,b)
        return max(q1,q2)