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Copy pathMultiply.java
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46 lines (43 loc) · 1.31 KB
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package leetcode.string;
/*
* @description: 43.字符串相乘
* @param: num1,num2非负整数
* @return: num1乘num2的结果
* @author: cp
* @date: 2020/8/28
*/
public class Multiply {
//todo
public String multiply(String num1, String num2) {
String zero = "0";
String one = "1";
//0和1比较特殊,先处理一下
if (num1.equals(zero) || num2.equals(zero))
return zero;
if (num1.equals(one))
return num2;
if (num2.equals(one))
return num1;
int length1 = num1.length();
int length2 = num2.length();
int length = Math.min(length1, length2);
int charLength = Math.max(length1, length2) + 1;
char[] result = new char[charLength];
result[0] = 0;
int carry = 0;
for (int i = 1; i <= length; i++) {
int tmp = multiplyChar(num1.charAt(length1 - i), num2.charAt(length2 - i));
result[charLength - i] = (char) (tmp % 10 + carry + '0');
carry = tmp / 10;
}
if (result[0] == 0)
return new String(result, 1, result.length);
return new String(result);
}
public int multiplyChar(char a, char b) {
return getAscii(a) * getAscii(b);
}
public int getAscii(char c) {
return c - '0';
}
}