2020年第十一届蓝桥杯第二场参赛 Java B 组真题
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2020年第十一届蓝桥杯第二场参赛 Java B 组真题
第一题
public class Q1 {
public static void main(String[] args) {
int sum = 0;
for (int i = 1; i <= 2020; i++) {
sum += count(i);
}
System.out.println(sum);
}
static int count(int num) {
int res = 0;
while (num > 0) {
int x = num % 10;
if (x == 2)
res++;
num /= 10;
}
return res;
}
}答案：624
第二题
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Q2 {
static int n = 6;
static int m = 6;
static char[][] mp = new char[6][6];
static String str;
static String target = "2020";
static int ans = 0;
public static void main(String[] args) throws FileNotFoundException {
// Scanner sc = new Scanner(System.in);
Scanner sc = new Scanner(new File("2020.txt"));
for (int i = 0; i < n; i++) {
char[] temp = sc.nextLine().toCharArray();
for (int j = 0; j < m; j++) {
mp[i][j] = temp[j];
}
}
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (mp[i][j] == '2') {
if (j + 3 < m) {
str = mp[i][j] + "" + mp[i][j+1] + "" + mp[i][j+2] + "" + mp[i][j+3];
if (target.equals(str))
ans++;
}
if (i + 3 < n) {
str = mp[i][j] + "" + mp[i+1][j] + "" + mp[i+2][j] + "" + mp[i+3][j];
if (target.equals(str))
ans++;
}
if (i + 3 < n && j + 3 < m) {
str = mp[i][j] + "" + mp[i+1][j+1] + "" + mp[i+2][j+2] + "" + mp[i+3][j+3];
if (target.equals(str))
ans++;
}
}
}
}
System.out.println(ans);
}
}第三题
public class Q3 {
static int MAX_N = 50;
static int[][] mp = new int[MAX_N][MAX_N];
static int cnt = 1;
public static void main(String[] args) {
for (int i = 1; i < MAX_N; i++) {
// 奇数行从 (i,1) 到 (1, i)
if (i % 2 != 0) {
for (int j = 0; j < i; j++) {
mp[i - j][1 + j] = cnt++;
}
} else {
for (int j =0; j < i; j++) {
mp[1 + j][i - j] = cnt++;
}
}
}
System.out.println(mp[20][20]);
}
}答案：761
第四题
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
public class Q4 {
static boolean[] book = new boolean[7];
static boolean[][] graph = new boolean[7][7];
static {
graph[0][1] = graph[0][5] = true;
graph[1][0] = graph[1][2] = graph[1][6] = true;
graph[2][1] = graph[2][3] = graph[2][6] = true;
graph[3][2] = graph[3][4] = true;
graph[4][3] = graph[4][5] = graph[4][6] = true;
graph[5][0] = graph[5][4] = graph[5][6] = true;
graph[6][1] = graph[6][2] = graph[6][4] = graph[6][5] = true;
}
static int ans = 0;
public static void main(String[] args) {
dfs(0);
System.out.println(ans);
}
static void judge() {
int cnt = 0;
boolean[] vis = new boolean[7];
Arrays.fill(vis, true);
Queue<Integer> queue = new LinkedList<>();
for (int i = 0; i < 7; i++) {
if (book[i]) {
vis[i] = false;
cnt++;
if (queue.isEmpty()) {
queue.add(i);
vis[i] = true;
}
}
}
if (queue.isEmpty()) return;
while (!queue.isEmpty()) {
int cur = queue.poll();
cnt--;
for (int i = 0; i < 7; i++) {
if (graph[cur][i] && !vis[i]) {
queue.add(i);
vis[i] = true;
}
}
}
if (cnt == 0) {
for (int i = 0; i < 7; i++)
if (book[i])
System.out.print((char)(i + 'a'));
System.out.println();
ans++;
}
}
static void dfs(int k) {
if (k == 7) {
judge();
return;
}
book[k] = true;
dfs(k + 1);
book[k] = false;
dfs(k + 1);
}
}答案：80
第六题
import java.util.Scanner;
public class Q6 {
static int n, max = 0, min = 100, sum = 0;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
for (int i = 0; i < n; i++) {
int x = sc.nextInt();
min = Math.min(min, x);
max = Math.max(max, x);
sum += x;
}
System.out.println(max);
System.out.println(min);
System.out.printf("%.2f", 0.01 * Math.round(100.0 * sum / n));
}
}第七题
import java.util.Scanner;
public class Q7 {
static int[] count = new int[128];
static String str;
static int max;
static char ans;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
str = sc.next();
for (int i = 0; i < str.length(); i++) {
char c = str.charAt(i);
count[c]++;
if (count[c] > max) {
max = count[c];
ans = c;
}
if (count[c] == max && c < ans) {
ans = c;
}
}
System.out.println(ans);
System.out.println(max);
}
}第八题
import java.util.Arrays;
import java.util.Scanner;
public class Q8 {
static int MAX_N = 105;
static int[][] mp = new int[MAX_N][MAX_N];
// dp[i][j][k]: 走到位置（i，j），向左走了 k 步时的最大和
static int[][][] dp = new int[MAX_N][MAX_N][MAX_N];
static int n, ans = 0;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= i; j++) {
mp[i][j] = sc.nextInt();
}
}
for (int i = 0; i < MAX_N; i++) {
for (int j = 0; j < MAX_N; j++) {
Arrays.fill(dp[i][j], -100000);
}
}
dp[1][1][0] = mp[1][1];
for (int i = 2; i <= n; i++) {
for (int j = 1; j <= i; j++) {
for (int k = 1; k < i; k++) {
dp[i][j][k] = Math.max(dp[i - 1][j][k - 1], dp[i - 1][j - 1][k]) + mp[i][j];
}
dp[i][j][0] = dp[i - 1][j - 1][0] + mp[i][j];
}
}
for (int j = 1; j <= n; j++) {
if (n % 2 == 0) {
ans = Math.max(ans, Math.max(dp[n][j][n / 2 - 1], dp[n][j][n / 2]));
} else {
ans = Math.max(ans, dp[n][j][n / 2]);
}
}
System.out.println(ans);
}
}第九题
import java.util.Scanner;
public class Q8 {
static char[] s;
static int[] pre = new int[128];
static int n;
static long ans = 0;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
s = sc.next().toCharArray();
n = s.length;
for (int i = 1; i <= n; i++) {
char c = s[i - 1];
ans += (long)(n - i + 1) * (long)(i - pre[c]);
pre[c] = i;
}
System.out.println(ans);
}
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