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Copy pathMathUtils.java
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138 lines (114 loc) · 3.36 KB
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package algorithm.math;
public class MathUtils {
/**
* 计算末尾0的个数
* 10!
*/
public static void calculateSizeOfLast0() {
int min = 1;
int max = 20;
int sizeOf0 = 0;
long value = 1;
for (int i = min; i <= max; i++) {
if (i % 5 == 0) {
sizeOf0++;
}
value = value * i;
}
System.out.println("sizeOf0:" + sizeOf0 + " value:" + value);
}
/**
* 计算表达式
* 如果加上()多层嵌套。嘿嘿
*/
public static void calculateExpress() {
String express = "1+(2-3*4)+2/2-4*4/2";
get(express);
}
/**
* 得到字符串内第一个()内的内容
*/
public static String get(String str) {
int index1 = str.indexOf("(");
int index2 = str.indexOf(")");
if (index1 < 0 || index2 < 0) {
return "";
}
str = str.substring(index1, index2 + 1);
System.out.println("str" + str);
return str;
}
/**
* 用来计算递归式的() 当前默认此表达式已经没有()了
*/
private static String calculate(String express) {
//先找到 * / ，将两边的数字计算完成之后 替换到这个字符串中
int indexMul = indexOf(express, "*");
int indexDivide = indexOf(express, "/");
int indexAdd = indexOf(express, "+");
int indexSub = indexOf(express, "-");
if (indexMul < Integer.MAX_VALUE || indexDivide < Integer.MAX_VALUE) {
//先做乘法
if (indexMul < indexDivide) {
}
}
return "";
}
private static int indexOf(String str, String key) {
int index = str.indexOf(key);
if (index < 0)
index = Integer.MAX_VALUE;
return index;
}
private static int calculate(String type, int num1, int num2) {
switch (type) {
case "+":
return num1 + num2;
case "-":
return num1 - num2;
case "*":
return num1 * num2;
case "/":
return num1 / num2;
}
return 0;
}
/**
* 比较两个数的大小 很繁琐的简单的算法
* 不能用- 也不用Math类的方法
*/
public static void compare(int a, int b) {
String strA = String.valueOf(a);
String strB = String.valueOf(b);
int indexA = strA.indexOf("-");
int indexB = strB.indexOf("-");
int length1 = strA.length();
int length2 = strB.length();
//A是负数
if (indexA >= 0) {
if (indexB >= 0) {
//B是负数
strA = strA.substring(1);
strB = strB.substring(1);
if (length1 > length2) {
System.out.println("a<b");
} else if (length1 < length2) {
System.out.println("a>b");
} else {
//遍历从高位开始比较
}
} else {
//B是正数
System.out.println("a<b");
}
//A是正数
} else {
//B是负数
if (indexB >= 0) {
System.out.println("a>b");
} else {
//todo pass
}
}
}
}