标签：java   leetcode   string   array   

题目

方法

将num1与0-9相乘的结果存到数组里面去，然后根据num2中的每一位，从数组中获取结果，注意添加0.

    public String sum(String num1, String num2) {
        int lenOne = num1.length();
        int lenTwo = num2.length();
        int i = lenOne - 1;
        int j = lenTwo - 1;
        int flag = 0;
        StringBuilder builder = new StringBuilder();
        while(i >= 0 && j >= 0) {
            int one = Integer.parseInt(num1.charAt(i) + "");
            int two = Integer.parseInt(num2.charAt(j) + "");
            int temp = one + two + flag;
            flag = temp / 10;
            builder.append(temp % 10);
            i--;
            j--;
        }
        while (i >= 0) {
            int one = Integer.parseInt(num1.charAt(i) + "");
            int temp = one + flag;
            flag = temp / 10;
            builder.append(temp % 10);
            i--;
        }
        while (j >= 0) {
            int two = Integer.parseInt(num2.charAt(j) + "");
            int temp = two + flag;
            flag = temp / 10;
            builder.append(temp % 10);
            j--;
        }
        if (flag != 0) {
        	builder.append(flag);
        }
        return builder.reverse().toString();
    }
    
    public String multiply(String num1, String num2) {
        if (num1 == null || num2 == null || num1.equals("") || num2.equals("")) {
            return null;
        }
        String[] pro = new String[10];
        int lenOne = num1.length();
        pro[0] = "0";
        pro[1] = num1;
        for (int k = 2; k < 10; k++) {
            int flag = 0;
            StringBuilder builder = new StringBuilder();
            for (int i = lenOne; i > 0; i--) {
                int temp = Integer.parseInt(num1.charAt(i - 1) + "");
                int acc = temp * k + flag;
                flag = acc / 10;
                builder.append(acc % 10);
            }
            if (flag != 0) {
                builder.append(flag);
            }
            pro[k] = builder.reverse().toString();
        }
//        System.out.println();
//        for (int i = 0; i < 10; i++) {
//        	System.out.println(pro[i]);
//        }
//        System.out.println();
        int lenTwo = num2.length();
        String product = "0";
        for (int i = 0; i < lenTwo; i++) {
            int digit = Integer.parseInt(num2.charAt(i) + "");
            String temp = pro[digit];
            if (!temp.equals(pro[0])) {
                for (int j = 0; j < lenTwo - 1 - i; j++) {
                    temp +="0";
                }
            }

            product = sum(product, temp);
        }
        return product;      
    }

Multiply Strings,布布扣,bubuko.com

Multiply Strings

标签：java   leetcode   string   array   

原文地址：http://blog.csdn.net/u010378705/article/details/30245871