备战蓝桥杯（java）（日益更新）

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前言：

将 c++ 代码 转换为 java 代码

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提示：以下是本篇文章正文内容：

一、c++ 到 java 须要注意的地方：

1. java中，如何实现像c++那样，typedef long long LL；
2. java中，如何实现像c++那样，const int N = 1e5 + 10;
3. java中，如何实现像c++那样，int n, m; int h[N], w[N];
4. java中，如何实现像c++那样，scanf(“%d%d”, &n, &m);
5. java中，如何实现像c++那样，#define x first #define y second typedef pair<int, int> PII;
6. java中，如何实现像c++那样int l = max(1, L - t), r = min((LL)m, (LL)L + t);
7. java中，如何实现像c++那样，sort(q, q+cnt)
8. java中，如何实现像c++那样， bool check(int mid)
9. java中，如何实现像c++那样，for(int i = 0; i < n; i ++) scanf(“%d%d”, &h[i], &w[i]);
10. java中，如何实现像c++那样，for(int i = 0; i < n; i ++) scanf(“%d%d”, &w[i].x, &w[i].y);

二、多练java代码：（用java代码写算法模版）

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1. acwing1277 分巧克力：

import java.util.Scanner;public class acwing1227分巧克力 {static final int N = 100010;// 全局常量static int n, m;// 全局变量static int h[] = new int[N];static int w[] = new int[N];// 二分“二段性”判断static boolean check(int mid){long res = 0;for(int i = 0; i < n; i ++){res += h[i] / mid * (w[i] / mid);if(res >= m) return true;}return false;}public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt();int m = scan.nextInt();// 输入方式！！！for (int i = 0; i < n; i++){h[i] = scan.nextInt();w[i] = scan.nextInt();}int l = 1, r = 100000;while(l < r){// int mid = (l + r + 1) / 2;int mid = l + (r - l + 1) / 2;if(check(mid)) l = mid;else r = mid - 1;}System.out.println(r);scan.close();}}// 思考：为什么答案不对？？？

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2. acwing5407 管道：

import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;public class acwing5407管道 {static class Pair {public final Integer first;public final Integer second;public Pair(Integer first, Integer second) {this.first = first;this.second = second;}}static int N = 100010;static int n, m;static Pair[] w = new Pair[N];// 位于Li阀门会在Si时刻打开static Pair[] q = new Pair[N];// 二分后，区间的左右端点static boolean check(int mid){int cnt = 0;for(int i = 0; i < n; i ++){int L = w[i].first, S = w[i].second;// 位置，打开时刻if(S <= mid){int t = mid - S;int l = (int) Math.max(1, L - t);int r = (int)Math.min((long)m, (long)L + t);q[cnt ++] = new Pair(l, r);// 注意}}// sort(q, q + cnt);// Java中没有直接对数组部分排序的方法，需要先将这部分元素提取出来Pair[] toSort = Arrays.copyOfRange(q, 0, cnt); // 提取前cnt个元素// 对提取出来的数组进行排序Arrays.sort(toSort, Comparator.comparingInt(i -> i.first));// 将排序后的元素放回原数组System.arraycopy(toSort, 0, q, 0, cnt);int st = -1, ed = -1;for(int i = 0; i < cnt; i ++){if(q[i].first <= ed + 1) ed = Math.max(ed, q[i].second);else{st = q[i].first;ed = q[i].second;}}return st == 1 && ed == m;}public static void main(String[] args) {Scanner scan = new Scanner(System.in);n = scan.nextInt();m = scan.nextInt();for (int i = 0; i < n; i++){int first = scan.nextInt();int second = scan.nextInt();w[i] = new Pair(first, second);}int l = 0, r = 2000000000;// 2e9while(l < r){// int mid = (long)l + r >> 1;int mid = (int)((long)l + r >> 1);if(check(mid)) r = mid;else l = mid + 1;}System.out.println(r);scan.close();}}

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3. acwing562 壁画

import java.util.Scanner;public class acwing562壁画 {static final int N = 100010;static int n;static int[] s = new int[N];static String str;public static void main(String[] args) {Scanner scan = new Scanner(System.in);int T = scan.nextInt();for(int cases = 1; cases <= T; cases ++){n = scan.nextInt();str = " " + scan.next();for(int i = 1; i <= n; i ++)s[i] = s[i - 1] + str.charAt(i) - '0';int res = 0;int m = (n + 1) / 2;for(int i = m; i <= n; i ++)res = Math.max(res, s[i] - s[i - m]);System.out.println("Case #" + cases + "：" + res);}scan.close();}
}
/*
4
4
1332
Case #1：6
4
9583
Case #2：14
3
616
Case #3：7
10
1029384756
Case #4：31*/

4. acwing1230 K倍区间

import java.util.Scanner;public class acwing1230K倍区间 {//定义全局变量：static final int N = 100010;static int n, k;static long[] s = new long[N];static int[] cnt = new int[N];public static void main(String[] args) {Scanner scan = new Scanner(System.in);n = scan.nextInt();k = scan.nextInt();for(int i = 1; i <= n; i ++){s[i] = scan.nextInt();s[i] += s[i - 1];// 前缀和}long res = 0;cnt[0] ++;for(int i = 1; i <= n; i ++){res += cnt[(int) (s[i] % k)];cnt[(int)s[i] % k] ++;}System.out.println(res);scan.close();}
}
/*
5 2
1
2
3
4
5
6*/

5. acwing4262 空调

import java.util.Scanner;public class acwing4262空调 {// 全局变量：static final int N = 100010;static int n;static  int[] a = new int[N];public static void main(String[] args) {Scanner scan = new Scanner(System.in);n = scan.nextInt();for(int i = 1; i <= n; i ++) a[i] = scan.nextInt();for(int i = 1; i <= n; i ++){int b = scan.nextInt();a[i] -= b;}for(int i = n; i >= 1; i --) a[i] -= a[i - 1];int pos = 0, neg = 0;for(int i = 1; i <= n; i ++){if(a[i] >0) pos += a[i];else neg -= a[i];}System.out.println(Math.max(pos, neg));scan.close();}
}
/*
5
1 5 3 3 4
1 2 2 2 1
5*/

6. acwing5396 棋盘

import java.util.Scanner;public class acwing5396棋盘 {static final int N = 2010;static int n, m;static int[][] b = new int[N][N];public static void main(String[] args) {Scanner scan = new Scanner(System.in);n = scan.nextInt();m = scan.nextInt();while (m-- > 0) {int x1 = scan.nextInt();int y1 = scan.nextInt();int x2 = scan.nextInt();int y2 = scan.nextInt();b[x1][y1] ++;b[x1][y2 + 1]--;b[x2 + 1][y1]--;b[x2 + 1][y2 + 1]++;}for (int i = 1; i <= n; i++) {for (int j = 1; j <= n; j++) {b[i][j] += b[i - 1][j] + b[i][j - 1] - b[i - 1][j - 1];System.out.print(b[i][j] & 1);}System.out.println();}scan.close();}
}

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总结

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