PTA-21班级团体训练欢乐赛（二）题解

// 判断输入的数组中是否包含指定值
bool contain(const char record[], int c) {
    for (int i = 0; record[i] != '\0'; ++i) {
        // 忽略大小写
        if (tolower(record[i]) == tolower(c)) return true;
    }
    return false;
}

int main() {
    char record[11];
    int size = 0;
    int c;
    recotd[10] = '\0';
    while (c = getchar(), c != '\n' && c != EOF) {
        // 如果c是字母并且record中不存在c，则将c放入数组中
        if (isalpha(c) && !contain(record, c)) {
            record[size++] = (char) c;
            // 如果数量达到10则直接退出
            if (size == 10) break;
        }
    }
    if (size != 10) printf("not found");
    else printf("%s", record);
    return 0;
}

// 判断指定数是否为质数
bool is(int n) {
    if (n == 1) return false;
    if (n == 2) return true;
    double d = sqrt(n) + 1;
    for (int i = 2; i < d; ++i) {
        if (n % i == 0) return false;
    }
    return true;
}

int main() {
    int record[1000];	// 记录质数
    int size = 0;	    // 质数的数量
    int m, n;
    scanf("%d %d", &m, &n);
    unsigned long long sum = 0;
    for (int i = m; i <= n; ++i) {
        if (is(i)) {
            record[size++] = i;
            sum += i;
        }
    }
    for (int i = 0; i != size; ++i) {
        if (i % 5 == 0 && i != 0) printf("\n");
        printf("%d ", record[i]);
    }
    printf("\namount=%d sum=%llu", size, sum);
    return 0;
}

int main() {
    int n;
    scanf("%d", &n);
    while (n--) printf("*");
    return 0;
}

int n;
int road[1000000];

// 求区间内的最优解
// 参数：
// 	 start - 起始位置（包括）
// 	 length - 长度
// 返回：
// 	 跳跃到的下标
int max(int start, int length) {
    int end = start + length;
    // 如果可以直接跳到终点则返回n
    if (end >= n) return n;
    int max = -1;
    int index = -1;
    // 找到可以跳的最远的点
    for (int i = start; i != end; ++i) {
        if (road[i] + i > max) {
            max = road[i] + i;
            index = i;
        }
    }
    return index;
}

int main() {
    scanf("%d", &n);
    for (int i = 0; i != n; ++i) scanf("%d", &road[i]);
    int result = 0;
    for (int i = 0; i != n;) {
        i = max(i + 1, road[i]);
        ++result;
    }
    printf("%d", result);
    return 0;
}

int main() {
    float f;
    scanf("%f", &f);
    int k = (int) f;
    float result = k * (f - k);
    printf("%.2f", result);
    return 0;
}

int main() {
    int n;
    scanf("%d", &n);
    int result = 0;
    while (n != 0) {
        if ((n & 1) == 1) ++result;
        n >>= 1;
    }
    printf("%d", result);
    return 0;
}

int main() {
    double result = 0;
    double r;
    scanf("%lf", &r);
    for (int i = 1;; ++i) {
        double k = 1.0 / (i * i);
        if (k < r) break;
        result += k;
    }
    printf("%.6f", sqrt(result * 6));
    return 0;
}

int main() {
    int weight[] = {7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2};
    char MS[] = {'1','0','X','9','8','7','6','5','4','3','2'};
    char id[19] = {'\0'};
    int t;
    scanf("%d", &t);
    int size = t;
    while (t--) {
        getchar();	//扔掉多余的换行符
        int result = 0;
        for (int i = 0; i != 17; ++i) {
            int temp = getchar();
            id[i] = (char) temp;
            int k = (temp - '0') * weight[i];
            result += k;
        }
        char m = MS[result % 11];
        id[17] = (char) getchar();
        if (toupper(id[17]) == m) --size;
        else printf("%s\n", id);
    }
    if (size == 0) printf("All passed");
    return 0;
}

int main() {
    int n;
    scanf("%d", &n);
    if (n < 100 || n > 999) return 0;
    n += (n / 100) * 1000;
    n *= 10;
    n += (n / 10) % 10;
    printf("%d", n);
    return 0;
}

int main() {
    int n;
    scanf("%d", &n);
    long long sum = 0;
    for (int i = 21; i <= n; ++i) sum += i;
    printf("sum = %lld", sum);
    return 0;
}