【第五天打卡。-白红宇

【第五天打卡。

阅读量：4883 次

发布时间：2019-06-11

本文共 2691 字，大约阅读时间需要 8 分钟。

Bag Sample

Compute the average and simple standard deviation of the double values on standard input

public class Stats {    public static void main (String[] args) {        Bag
      
        numbers = new Bag
       
        ();        while(!StdIn.isEmpty)             numbers.add(StdIn.readDouble());        int N = numbers.size();        double sum = 0.0;        for (double x : numbers)            sum += x;        double mean = sum/N;        sum = 0.0;        for (double x : numbers)            sum += (x-mean)*(x-mean);        double std = Math.sqrt(sum/(N-1));        StdOut.printf("Mean: %.2f\n", mean);        StdOut.printf("Std dev: %.2f\n", std);     }}

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FIFO Queues

Sample queue client

public static int[] readInts (String name) {    In in = new In(name);    Queue
      
        q = new Queue
       
        ();    while(!in.isEmpty())         q.enqueue(in.readInt());    int N = q.size();    int[] a = new int[N];    for(int i = 0; i < N; i++)         a[i] = q.dequeue();    return a;}

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LIFO Stacks

Sample stack client

public class Reverse {    public static void main (String[] args) {        Stack
      
        stack = new Stack
       
        ();        while(!StdIn.isEmpty())             stack.push(StdIn.readIn());        for(int i : stack)            StdOut.println(i);    }}

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Dijkstra's Two-Stack Algorithm for Expression Evaluation

public class evaluate {    public static void main(String[] args) {        Stack
      
        ops = new Stack
       
        ();        Stack
        
          vals = new Stack
         
          ();        while (!StdIn.isEmpty){            String s = StdIn.readString();            if (s.equals("("));            else if (s.equals("+"))    ops.push(s);            else if (s.equals("-"))     ops.push(s);            else if (s.equals("*"))    ops.push(s);            else if (s.equals("/"))     ops.push(s);            else if (s.equals(")"))     ops.push(s);            else if (s.equals("sqrt")) ops.push(s);            else if (s.equals(")")) {                String op = ops.pop();                Double v = vals.pop();                if (op.equals("+"))    v = vals.pop() + v;                else if (op.equals("-")) v = vals.pop() - v;                else if (op.equals("*")) v = vals.pop() * v;                else if (op.equals("/")) v = vals.pop() / v;                else if (op.equals("sqrt")) v = Math.sqrt(v);                vals.push(v);            }            else vals.push(Double.parseDouble(s));        }        StdOut.println(vals.pop());    }    }