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'; } }