Java [Leetcode 43]Multiply Strings

题目描述：

Given two numbers represented as strings, return multiplication of the numbers as a string.

Note: The numbers can be arbitrarily large and are non-negative.

解题思路：

设置数组记录单个位置相乘的结果，最后负责相加进位。

代码如下：

public class Solution {

    public String multiply(String num1, String num2) {

		int num1Length = num1.length();

		int num2Length = num2.length();

		int d1, d2;

		int carry = 0;

		int temp;

		int[] caculate = new int[num1Length + num2Length];

		StringBuilder sb = new StringBuilder();

		for (int i = num1.length() - 1; i >= 0; i--) {

			d1 = num1.charAt(i) - '0';

			for (int j = num2.length() - 1; j >= 0; j--) {

				d2 = num2.charAt(j) - '0';

				caculate[i + j + 1] += d1 * d2;

			}

		}

		for (int i = caculate.length - 1; i >= 0; i--) {

			temp = (caculate[i] + carry) % 10;

			carry = (caculate[i] + carry) / 10;

			caculate[i] = temp;

		}

		for (int num : caculate)

			sb.append(num);

		while (sb.length() > 1 && sb.charAt(0) == '0') {

				sb.deleteCharAt(0);

		}

		return sb.toString();

	}

}

巴特西

Java [Leetcode 43]Multiply Strings

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