local UF = {} UF.create = function(self, n) self.parent = {} for i = 1, n do self.parent[i] = i end end UF.getroot = function(self, idx) local parent = self.parent local idx_update = idx while parent[idx] ~= idx do idx = parent[idx] end while parent[idx_update] ~= idx do parent[idx_update], idx_update = idx, parent[idx_update] end return idx end UF.unite = function(self, a, b) local ra = self:getroot(a) local rb = self:getroot(b) self.parent[b], self.parent[rb] = ra, ra end UF.new = function(n) local obj = {} setmetatable(obj, {__index = UF}) obj:create(n) return obj end local n, q = io.read("*n", "*n") local uf = UF.new(n) for i = 1, n do local p = io.read("*n") if 0 < p then uf:unite(p, i) end end for iq = 1, q do local a, b = io.read("*n", "*n") local ra = uf:getroot(a) local rb = uf:getroot(b) print(a == b and "Yes" or "No") end