fix(题目列表): 「随便来一道」常抽到用自己的语言做不了的题，老师那边「只看没做完」开了看不出藏了什么

- 随便来一道：按学生在编辑器里上次用的语言挑（没用过按 Python），C 学生不再抽到 Python 专用题和 SQL 题，Python 学生不再抽到 SQL 题；选了 SQL 知识点或 SQL 类型才从 SQL 题里抽。也跟着「全部类型」的筛选走
- 老师那一版去掉「只看没做完」：没有状态列，开了只是题少了
- 题目页「相似题目」：流程图评到 A / S 的题也算做对，不再推荐，和列表打勾一个口径

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/src/routes/problem.ts

@@ -1,4 +1,5 @@
 import {
+  normalizeLanguage,
   problemListSortSchema,
   problemTypeFilterSchema,
   type ProblemAuthor,
@@ -6,6 +7,7 @@ import {
   type ProblemList,
   type ProblemListItem,
   type ProblemProgress,
+  type ProblemTypeFilter,
   type Tag,
 } from "@oj2/contract"
 import {
@@ -81,6 +83,15 @@ async function getProblemTags(problemIds: number[]) {
   return result
 }
 
+/** 「全部类型」下拉的筛选条件，列表和「随便来一道」共用 */
+function typeFilter(type: ProblemTypeFilter | undefined) {
+  if (type === "reference") return eq(schema.problem.showFlowchart, true)
+  if (type === "flowchart") return eq(schema.problem.allowFlowchart, true)
+  if (type === "ast") return sql`${schema.problem.astRules} is not null`
+  if (type === "sql") return sql`${schema.problem.languages} @> '["SQL"]'::jsonb`
+  return undefined
+}
+
 type ProblemStates = Awaited<ReturnType<typeof problemStates>> | null
 type UserCounts = Awaited<ReturnType<typeof problemUserCounts>>
 
@@ -155,10 +166,8 @@ problemRoutes.get("/problems", optionalAuth, async (c) => {
       ),
     )
   }
-  if (type === "reference") filters.push(eq(schema.problem.showFlowchart, true))
-  if (type === "flowchart") filters.push(eq(schema.problem.allowFlowchart, true))
-  if (type === "ast") filters.push(sql`${schema.problem.astRules} is not null`)
-  if (type === "sql") filters.push(sql`${schema.problem.languages} @> '["SQL"]'::jsonb`)
+  const byType = typeFilter(type)
+  if (byType) filters.push(byType)
 
   const states = user ? await problemStates(user.id) : null
   if (undone && states && states.solved.size > 0)
@@ -254,12 +263,22 @@ problemRoutes.get("/problem-tags", async (c) => {
 })
 
 /**
- * 「随便来一道」：范围是当前知识点（不传就是全部），先挑自己还没做对的简单 / 中等题，
- * 没有就放宽到没做对的困难题，再没有就随便一道（全做对了也给一道，不让按钮落空）。
+ * 「随便来一道」：范围是当前知识点和类型（不传就是全部），先挑能用自己的语言做的、
+ * 还没做对的简单 / 中等题，没有就一档档放宽：没做对的困难题 → 做对过的
+ * （全做对了也给一道，不让按钮落空）→ 别的语言的题。
+ *
+ * 语言是前端记着的「上次用的语言」，没有就是 Python。不按语言挑的话，C 学生大约每
+ * 9 次就抽到 1 道没有 C 的题（Python 专用题和 SQL 题）。语言排在最前、而不是筛掉：
+ * 选了「SQL」知识点时没有一道能用 Python 做，照样得抽一道 SQL 题出来。
  */
 problemRoutes.get("/problems/random", optionalAuth, async (c) => {
   const user = c.get("user")
   const tag = c.req.query("tag")?.trim()
+  const type = problemTypeFilterSchema.safeParse(c.req.query("type")).data
+  // 上次用的是 SQL（刚做完一道 SQL 题）不算偏好：SQL 题一共 9 道，照它挑就成了「随便来一道
+  // SQL」。要 SQL 题的人会选「SQL」知识点或类型，那时按上面说的照样抽得到
+  const saved = normalizeLanguage(c.req.query("language"))
+  const language = saved && saved !== "SQL" && saved !== "Flowchart" ? saved : "Python"
   const states = user ? await problemStates(user.id) : null
   const solved = states ? [...states.solved] : []
   const [row] = await db
@@ -282,11 +301,13 @@ problemRoutes.get("/problems/random", optionalAuth, async (c) => {
                 .where(eq(schema.problemTag.name, tag)),
             )
           : undefined,
+        typeFilter(type),
       ),
     )
     // 没做对过题（没登录、新生）就不排这一项。别拿 sql`1` 占位：ORDER BY 里的整数常量是
     // 「按第 1 列排」，会先按题号排、random() 形同虚设，每次都是同一道
     .orderBy(
+      desc(sql`${schema.problem.languages} @> ${JSON.stringify([language])}::jsonb`),
       ...(solved.length ? [asc(inArray(schema.problem.id, solved))] : []),
       asc(sql`${schema.problem.difficulty} = 'High'`),
       sql`random()`,
@@ -337,11 +358,13 @@ problemRoutes.get("/problems/:displayId/similar", optionalAuth, async (c) => {
   // 「已 AC 的不再推荐」必须下推到 SQL。早先是先 limit(5) 再在内存里筛，刷题多的
   // 学生 5 条候选能被筛到只剩一两条、甚至清零（前端 v-if 一空整块就不渲染）——
   // 而这个接口恰好只在**刚 AC** 或**连挂三次**时才被调用，正是候选最容易全中的时候。
-  const statuses = await getProblemStatuses(c.get("user")?.id)
-  const solvedIds = Object.entries(statuses)
-    .filter(([, value]) => asRecord(value).status === JudgeStatus.ACCEPTED)
-    .map(([key]) => Number(key))
-    .filter((id) => Number.isInteger(id))
+  // 做对了的和题目列表同一个口径：画流程图的题，流程图评到 A / S 也算（problemStates）
+  const user = c.get("user")
+  const [statuses, states] = await Promise.all([
+    getProblemStatuses(user?.id),
+    user ? problemStates(user.id) : null,
+  ])
+  const solvedIds = states ? [...states.solved] : []
   // difficulty 是 text（Low / Mid / High），直接 order by 走的是字典序 ——
   // High 排在 Low 前面，「由易到难」会变成「最难的先上」。按语义显式排。
   const difficultyRank = sql`case ${schema.problem.difficulty} when 'Low' then 0 when 'Mid' then 1 else 2 end`
@@ -388,7 +411,7 @@ problemRoutes.get("/problems/:displayId/similar", optionalAuth, async (c) => {
   const [tags, counts] = await Promise.all([getProblemTags(ids), problemUserCounts(ids)])
   return success(
     c,
-    rows.map((row) => listItem(row, tags, statuses, null, counts)),
+    rows.map((row) => listItem(row, tags, statuses, states, counts)),
   )
 })
 

apps/web/src/oj/api.ts

@@ -100,9 +100,12 @@ export function getProblemProgress() {
   return api.get<ProblemProgress | null>("problems/progress")
 }
 
-/** 「随便来一道」：当前知识点里先挑自己没做对的简单 / 中等题，返回题号 */
-export function getRandomProblem(tag: string) {
-  return api.get<string>("problems/random", { params: tag ? { tag } : {} })
+/**
+ * 「随便来一道」：当前知识点和类型里，先挑能用 language 做的、自己没做对的简单 / 中等题，
+ * 返回题号。空串的参数拦截器会去掉
+ */
+export function getRandomProblem(params: { tag: string; type: string; language: string }) {
+  return api.get<string>("problems/random", { params })
 }
 
 export function getAuthors(all = false) {

apps/web/src/oj/problem/list.vue

@@ -4,6 +4,7 @@ import type { ProblemProgress, ProblemTypeFilter, Tag } from "@oj2/contract"
 import { useRouteQuery } from "@vueuse/router"
 import { useThemeVars } from "naive-ui"
 import { getAuthors, getProblemList, getProblemProgress, getRandomProblem } from "oj/api"
+import { useCodeStore } from "oj/store/code"
 import { useTone } from "oj/submission/composables/tone"
 import { STORAGE_KEY } from "utils/constants"
 import storage from "utils/storage"
@@ -54,6 +55,7 @@ const userStore = useUserStore()
 const authStore = useAuthModalStore()
 const theme = useThemeVars()
 const tone = useTone()
+const codeStore = useCodeStore()
 const { isDesktop, isMobile } = useBreakpoints()
 
 const { query } = usePagination<ProblemQuery>(
@@ -69,11 +71,6 @@ const { query } = usePagination<ProblemQuery>(
   { defaultLimit: 30 },
 )
 
-const undoneOn = computed({
-  get: () => query.undone === "1",
-  set: (on: boolean) => (query.undone = on ? "1" : ""),
-})
-
 const problems = ref<ProblemRow[]>([])
 const total = ref(0)
 const loaded = ref(false)
@@ -86,6 +83,12 @@ const teacher = computed(() => userStore.isTeacherOrAbove)
 const showStatus = computed(() => userStore.isAuthed && !teacher.value)
 const mine = computed(() => (showStatus.value ? progress.value : null))
 
+// 老师那一版没有这个开关：没有状态列，开了也看不出藏了哪些题。带着 ?undone=1 进来也当没开
+const undoneOn = computed({
+  get: () => query.undone === "1" && !teacher.value,
+  set: (on: boolean) => (query.undone = on ? "1" : ""),
+})
+
 const tagByName = computed(() => new Map(tags.value.map((t) => [t.name, t])))
 const currentTag = computed(() => tagByName.value.get(query.tag) ?? null)
 const startTag = computed(() => tagByName.value.get(START_TAG) ?? null)
@@ -279,7 +282,12 @@ const picking = ref(false)
 async function pickRandom() {
   picking.value = true
   try {
-    const id = await getRandomProblem(query.tag)
+    const id = await getRandomProblem({
+      tag: query.tag,
+      type: query.type,
+      // 只挑能用自己的语言做的题：学生在编辑器里上次用的语言，没用过就是 Python
+      language: codeStore.preferredLanguage(),
+    })
     router.push("/problem/" + id)
   } finally {
     picking.value = false
@@ -511,8 +519,9 @@ const gridColumns = computed(() =>
             :consistent-menu-width="false"
             :options="sortOptions"
           />
-          <span class="vsep"></span>
+          <span v-if="!teacher" class="vsep"></span>
           <label
+            v-if="!teacher"
             class="undone"
             :class="{ disabled: !userStore.isAuthed }"
             :title="userStore.isAuthed ? '做对的题藏起来' : '登录后才能用'"
@@ -665,7 +674,7 @@ const gridColumns = computed(() =>
           @update:value="(v: string | null) => (query.author = v ?? '')"
         />
         <n-select v-model:value="query.sort" size="small" :options="sortOptions" />
-        <label class="undone" :class="{ disabled: !userStore.isAuthed }">
+        <label v-if="!teacher" class="undone" :class="{ disabled: !userStore.isAuthed }">
           <n-switch v-model:value="undoneOn" size="small" :disabled="!userStore.isAuthed" />
           只看没做完
         </label>