最近做了几套华为的机试题,今天有时间,把之前写的几套代码全都贴出来。题目都只记得个大概,将就着看吧,不过代码都是完整的,自认为写的还行。
题目描述
大概意思是:实现一个加减乘的计算。给定的样式是一个字符串,且该字符串为正确的字符串;需要运算的数字均为正数,且每个数字前只有一个运算符。
Java代码
初始思路比较笨,对字符串从左到右一个一个的做判断。分割出数字和运算符号后,先算乘法,再算加减。写完后回头看代码,都有点郁闷了,听上去这么简单的功能,怎么不小心,代码就这么长了呢:
import java.util.Scanner;
import java.util.Stack;
public class Main2 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String line = scanner.nextLine();
Stack<String> splitItems = getSplitItems(line);
int res = getCalculationResult(splitItems);
scanner.close();
System.out.println(res);
}
public static Stack<String> getSplitItems(String line) {
Stack<String> stackS = new Stack<String>();
char[] charS = line.toCharArray();
int accu = 0;
boolean isNumReady = false;
for(char c:charS) {
if(c>='0' && c<='9') {
accu = accu*10 + (int)(c-'0');
isNumReady = true;
}else {
if(isNumReady) {
stackS.add(String.valueOf(accu));
}
if(c=='+'||c=='-'||c=='*'){
stackS.add(String.valueOf(c));
}else {
return null;
}
isNumReady = false;
accu = 0;
}
}
if(isNumReady) {
stackS.add(String.valueOf(accu));
}
return stackS;
}
public static int getCalculationResult(Stack<String> stack) {
if(stack==null) {
return -1;
}
Stack<String> helpStack = new Stack<String>();
while(!stack.isEmpty()) {
String item = stack.pop();
if(item.equals("*")) {
int mult = Integer.parseInt(stack.pop()) * Integer.parseInt(helpStack.pop());
helpStack.push(String.valueOf(mult));
}else {
helpStack.push(item);
}
}
int resNum = Integer.valueOf(helpStack.pop());
while(!helpStack.isEmpty()) {
String s = helpStack.pop();
if(s.equals("+")) {
resNum += Integer.parseInt(helpStack.pop());
}else if(s.equals("-")) {
resNum -= Integer.parseInt(helpStack.pop());
}
}
return resNum;
}
}
刚突然灵光一闪,我为什么不能用符号“+-*”来直接分隔出数字,用数字分隔出我需要的符号呢,这样分别获得存储数字的栈和存储符号的栈,计算起来岂不是更Easy?以下是我实现的代码:
import java.util.Scanner;
import java.util.Stack;
public class Main3 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String line = scanner.nextLine();
Stack<Integer> splitNums = getSplitNums(line);
Stack<String> splitStrs = getSplitStrs(line);
int res = getCalculationResult(splitNums, splitStrs);
scanner.close();
System.out.println(res);
}
public static Stack<Integer> getSplitNums(String line) {
Stack<Integer> stackS = new Stack<>();
String[] strArray = line.split("\\+|-|\\*");
for(String s:strArray) {
stackS.push(Integer.parseInt(s));
}
return stackS;
}
public static Stack<String> getSplitStrs(String line){
Stack<String> stackS = new Stack<>();
String[] strArray = line.split("[0-9]+");
for(String s:strArray) {
if(!s.equals("")){
stackS.push(s);
}
}
return stackS;
}
public static int getCalculationResult(Stack<Integer> nums, Stack<String> symbles) {
Stack<Integer> numsStack = new Stack<>();
Stack<String> symStack = new Stack<>();
numsStack.push(nums.pop());
while(!symbles.isEmpty()) {
String symble = symbles.pop();
if(symble.equals("*")) {
numsStack.push(nums.pop() * numsStack.pop());
}else {
symStack.push(symble);
numsStack.push(nums.pop());
}
}
while(!symStack.isEmpty()) {
int num = numsStack.pop();
String symble = symStack.pop();
if(symble.equals("+")){
numsStack.push(num + numsStack.pop());
}else if(symble.equals("-")) {
numsStack.push(num - numsStack.pop());
}
}
return numsStack.pop();
}
}