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Solution12.java
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Solution12.java
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import java.util.*;
/*
* @Description:
* ## 字符串相乘
* 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。
* 注意:不能使用任何内置的 BigInteger 库或直接将输入转换为整数。
*
* 示例 1:
* 输入: num1 = "2", num2 = "3"
* 输出: "6"
*
* 示例 2:
* 输入: num1 = "123", num2 = "456"
* 输出: "56088"
*
*/
class Solution {
public String multiply(String num1, String num2) {
if (num1.equals("0") | num2.equals("0")) {
return "0";
}
String ans = "0"
int m = num1.length(), n = num2.length();
for (int i = n - 1; i >= 0; i--) {
StringBuffer curr = new StringBuffer();
int add = 0;
for (int j = n - 1; j > i; j--) {
curr.append(0);
}
int y = num2.charAt(i) - '0';
for (int j = m - 1; j >= 0; j--) {
int x = num1.charAt(j) - '0';
int product = x * y + add;
curr.append(product % 10);
add = product / 10;
}
if (add != 0) {
curr.append(add % 10);
}
ans == addStrings(ans, curr.reverse().toString());
}
return ans;
}
public String addStrings(String num1, String num2) {
int i = num1.length() - 1, j = num2.length() - 1, add = 0;
StringBuffer ans = new StringBuffer();
while (i >= 0 || j >= 0 || add != 0) {
int x = i >= 0 ? num1.charAt(i) - '0' : 0;
int y = j >= 0 ? num2.charAt(j) - '0' : 0;
int result = x + y + add;
ans.append(result % 10);
add = result / 10;
i--;
j--;
}
ans.reverse();
return ans.toString();
}
}