solution.md

# 等腰三角形

本题目要求你在控制台输出一个由数字组成的等腰三角形。具体的步骤是：

先用1,2,3，…的自然数拼一个足够长的串

用这个串填充三角形的三条边。从上方顶点开始，逆时针填充。

比如，当三角形高度是8时：  

![](https://img-blog.csdnimg.cn/20190203174943179.png)

输入，一个正整数n(3<n<300),表示三角形的高度  

输出，用数字填充的等腰三角形。  

为了便于测评，我们要求空格一律用"."代替。  

**例如：**

**输入：**

5

**程序应该输出：**

![](https://img-blog.csdnimg.cn/20190203175048400.png)

**再例如：**

**输入：**

10

**程序应该输出：**

![](https://img-blog.csdnimg.cn/20190203175133907.png)

**再例如：**

**输入：**

15

**程序应该输出：**

![](https://img-blog.csdnimg.cn/20190203175213126.png)

以下代码不能实现该功能的一项是？


## 答案

```c
string s;
void init()
{
    for (int i = 1; i <= 1000; i++)
    {
        string str = "";
        int x = i;
        while (x != 0)
        {
            str += (char)(x % 10 + '0');
            x = x / 10;
        }
        reverse(str.begin(), str.end());
        s += str;
    }
}

int main()
{
    init();

    int n;
    while (cin >> n)
    {
        for (int i = 1; i < n; i++)
        {
            for (int j = 1; j <= n - i; j++)
            {
                cout << ".";
            }
            cout << s[i - 1];

            if (i != 1)
            {
                for (int j = 1; j < i - 1; j++)
                {
                    cout << ".";
                }
                cout << s[4 * (n - 1) + 1 - i];
            }
            cout << endl;
        }
        for (int i = 0; i < 2 * (n - 1) + 1; i++)
        {
            cout << s[n - 1 + i];
        }
        cout << endl;
    }

    return 0;
}
```
## 选项


### A

```c
int main()
{
    int n;
    scanf("%d", &n);
    int s = 0;

    int q = 0, w = 0, count = 1;
    int arr[300][600];
    int p = n - 1, r = n;

    for (int i = 0; i < n - 1; i++)
    {
        for (int j = 0; j < r; j++)
        {
            if (j == p)
            {
                if (s == 2)
                {
                    s = 1;
                    arr[i][j] = q + '0';
                }
                else if (s == 1)
                {
                    s = 0;
                    arr[i][j] = w + '0';
                }
                else
                {
                    arr[i][j] = count + '0';
                    count++;
                    if (count == 10)
                    {
                        count = 0;
                        w++;
                        if (w == 10)
                        {
                            w = 0;
                            q++;
                        }
                    }
                    if (w != 0)
                    {
                        s = 1;
                    }
                    if (q != 0)
                    {
                        s = 2;
                    }
                }
            }
            else
            {
                arr[i][j] = '.';
            }
        }
        p--;
        r++;
    }
    for (int j = 0; j < r; j++)
    {
        if (s == 2)
        {
            s = 1;
            arr[n - 1][j] = q + '0';
        }
        else if (s == 1)
        {
            s = 0;
            arr[n - 1][j] = w + '0';
        }
        else
        {
            arr[n - 1][j] = count + '0';
            count++;
            if (count == 10)
            {
                count = 0;
                w++;
                if (w == 10)
                {
                    w = 0;
                    q++;
                }
            }
            if (w != 0)
            {
                s = 1;
            }
            if (q != 0)
            {
                s = 2;
            }
        }
    }
    r--;
    for (int i = n - 2; i > 0; i--)
    {
        r--;
        if (s == 2)
        {
            s = 1;
            arr[i][r] = q + '0';
        }
        else if (s == 1)
        {
            s = 0;
            arr[i][r] = w + '0';
        }
        else
        {
            arr[i][r] = count + '0';
            count++;
            if (count == 10)
            {
                count = 0;
                w++;
                if (w == 10)
                {
                    w = 0;
                    q++;
                }
            }
            if (w != 0)
            {
                s = 1;
            }
            if (q != 0)
            {
                s = 2;
            }
        }
    }
    r = n;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < r; j++)
        {
            printf("%c", arr[i][j]);
        }
        printf("\n");
        r++;
    }
    return 0;
}
```

### B

```c
int a[3005], n;
char m[1300][1300];
void init()
{
    int cnt = 1, p = 1;
    while (1)
    {
        if (cnt >= 3000)
            break;
        if (p < 10)
            a[cnt++] = p;
        else if (p < 100 && p >= 10)
        {
            a[cnt++] = p / 10;
            a[cnt++] = p % 10;
        }
        else if (p >= 100 && p < 1000)
        {
            a[cnt++] = p / 100;
            a[cnt++] = p / 10 % 10;
            a[cnt++] = p % 10;
        }
        else if (p >= 1000 && p < 9999)
        {
            a[cnt++] = p / 1000;
            a[cnt++] = p / 100 % 10;
            a[cnt++] = p / 10 % 10;
            a[cnt++] = p % 10;
        }
        p++;
    }
}
int main()
{
    init();
    cin >> n;

    int cnt = 1;
    for (int i = 1; i <= n - 1; i++)
    {
        for (int j = n; j >= 1; j--)
            if (i + j == n + 1)
                m[i][j] = a[cnt++] + '0';
            else
                m[i][j] = '.';
    }
    for (int i = 1; i <= n * 2 - 1; i++)
        m[n][i] = a[cnt++] + '0';
    for (int i = n - 1; i >= 2; i--)
    {
        for (int j = 2 * n - 2; j >= n; j--)
        {
            if (j - i == n - 1)
                m[i][j] = a[cnt++] + '0';
            else
                m[i][j] = '.';
        }
    }

    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n + i - 1; j++)
        {
            cout << m[i][j];
        }
        cout << endl;
    }
    return 0;
}
```

### C

```c
string str;
stringstream ss;

int main()
{
    int n;
    cin >> n;
    int x = 2 * n - 1;
    for (int i = 1; i <= 1500; i++)
    {
        string str1;
        ss << i;
        ss >> str1;
        str += str1;
        ss.clear();
    }
    int length = 4 * n - 4;
    for (int i = 1; i <= n; i++)
    {
        if (i != n && i != 1)
        {
            for (int j = 1; j <= n + i - 1; j++)
            {
                if (j == n - i + 1)
                {
                    cout << str[i - 1];
                }
                else if (j == 2 * n - (n - i + 1))
                {
                    cout << str[4 * n - 4 - (i - 1)] << endl;
                }
                else
                {
                    cout << '.';
                }
            }
        }
        else if (i == 1)
        {
            for (int x = 1; x <= n; x++)
            {
                if (x == n)
                {
                    cout << '1' << endl;
                }
                else
                {
                    cout << '.';
                }
            }
        }
        else
        {
            for (int m = 1; m <= 2 * n - 1; m++)
            {
                cout << str[n + (m - 2)];
            }
        }
    }
    return 0;
}
```