【LeetCode】#43字符串相乘(Multiply Strings)
题目描述
给定两个以字符串形式表示的非负整数 num1 和 num2，返回 num1 和 num2 的乘积，它们的乘积也表示为字符串形式。
示例
示例 1:
输入: num1 = “2”, num2 = “3”
输出: “6”
示例 2:
输入: num1 = “123”, num2 = “456”
输出: “56088”
Description
Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.
Example
Example 1:
Input: num1 = “2”, num2 = “3”
Output: “6”
Example 2:
Input: num1 = “123”, num2 = “456”
Output: “56088”
解法
class Solution{
public String multiply(String num1, String num2){
char[] value = new char[num1.length()+num2.length()];
for(int i=num1.length()-1; i>=0; i--){
for(int j=num2.length()-1; j>=0; j--){
value[i+j+1] += (num1.charAt(i)-'0')*(num2.charAt(i)-'0');
}
}
int carry = 0;
for(int i=value.length-1; i>=0; i--){
value[i] += carry;
carry = value[i]/10;
value[i] %= 10;
}
int beginIndex = 0;
while(beginIndex<value.length-1 && value[beginIndex]==0){
beginIndex++;
}
for(int i=beginIndex; i<value.length; i++){
value[i] += '0';
}
return new String(value, beginIndex, value.length-beginIndex);
}
}