笔试算法总结

题目1

使用 StringBuilder 模拟栈的行为，通过判断相邻2个字符是否相同，如果相同就进行删除

public class Main {public static String fun(String s) {if (s == null || s.length() <= 1) return s;StringBuilder builder = new StringBuilder(); // 使用StringBuilder模拟栈for (char c : s.toCharArray()) {if (builder.length() > 0 && builder.charAt(builder.length() - 1) == c) {builder.deleteCharAt(builder.length() - 1);} else {builder.append(c);}}return builder.toString();}public static void main(String[] args) {Scanner scanner = new Scanner(System.in);String s = scanner.nextLine();System.out.println(fun(s));}
}

题目2

public class Main {public static int climbStairs(int n) {if (n <= 2) {return n;}int[] dp = new int[n + 1]; // 动态规划数组dp[1] = 1;dp[2] = 2;for (int i = 3; i <= n; i++) {dp[i] = dp[i - 1] + dp[i - 2]; // 状态转移方程}return dp[n];}public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int n = scanner.nextInt();System.out.println(climbStairs(n));}
}

题目3

 public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int N = scanner.nextInt();int n = N;ArrayList<Integer> list = new ArrayList<>(N);while (n > 0) {list.add(scanner.nextInt());n -= 1;}ArrayList<Integer> list1 = new ArrayList<>(N);for (int i = 0; i < N; i++) {list1.add(0);}int res = 0;// 每次从每个口袋中取列表中最小值个糖果（0不管）while (!list1.equals(list)) {int min = Integer.MAX_VALUE;for (Integer i : list) {if (i == 0) continue;if (i < min) min = i;}for (int i = 0; i < list.size(); i++) {if (list.get(i) == 0) continue;list.set(i, list.get(i) - min);}res+=1;}System.out.println(res);}
}