题目：

题解：

struct NestedIterator {
    int *vals;
    int size;
    int cur;
};

void dfs(struct NestedIterator *iter, struct NestedInteger **nestedList, int nestedListSize) {
    for (int i = 0; i < nestedListSize; i++) {
        if (NestedIntegerIsInteger(nestedList[i])) {
            (iter->vals)[(iter->size)++] = NestedIntegerGetInteger(nestedList[i]);
        } else {
            dfs(iter, NestedIntegerGetList(nestedList[i]), NestedIntegerGetListSize(nestedList[i]));
        }
    }
}

struct NestedIterator *nestedIterCreate(struct NestedInteger **nestedList, int nestedListSize) {
    struct NestedIterator *ret = malloc(sizeof(struct NestedIterator));
    ret->vals = malloc(sizeof(int) * 20001);
    ret->size = 0;
    ret->cur = 0;
    dfs(ret, nestedList, nestedListSize);
    return ret;
}

bool nestedIterHasNext(struct NestedIterator *iter) {
    return iter->cur != iter->size;
}

int nestedIterNext(struct NestedIterator *iter) {
    return (iter->vals)[(iter->cur)++];
}

void nestedIterFree(struct NestedIterator *iter) {
    free(iter->vals);
    free(iter);
}