输入一个数字n，打印1到n位数的最大值。eg：n=3，代表打印1-999之间的数字

桃扇骨 2021-09-16 15:18 224阅读 0赞

相关解决：

package com.swordRefersToOffer;
    
    import java.util.Arrays;
    
    /**
     * @author 凌龙
     * @date 2018/9/28
     */
    
    public class Test {
        public static void main(String[] args) {
            Test test = new Test();
    //        test.printToMax(1);
            test.printToMax2(2);
        }
        /**
         *方法一：
         */
    
        /**字符串上模拟加法     *      * @param n     */
        public void printToMax(int n){
            if(n < 0)
                return;
            char[] number = new char[n];
            //    初始化       //    for(int i = 0; i < n; i++) number[i] = '0';
            Arrays.fill(number, '0');//字符串填充0;
            while(!increment(number)){
                printNumber(number);
            }
            return;
        }
    
        public boolean increment(char[] num){
            boolean isOverflow = false;
            int size = num.length;
            int carry = 0;
            for(int i = size - 1; i >= 0; i--){
                int temp = num[i] - '0' + carry;
                if(i == size - 1)
                    temp++;
                if(temp >= 10){
                    if(i == 0) //最高位溢出
                        isOverflow = true;
                    else{
                        temp -= 10;
                        carry = 1;
                        num[i] = (char) ('0' + temp);
                    }
                }else{
                    num[i] = (char)('0' + temp);
                    break;
                }
            }
            return isOverflow; }
    
    
        public void printNumber(char[] num){
            int size = num.length;
            int i = 0;
            while(i < size && num[i] == '0') //i < size在前，否则越界
                i++;      //char[] printNum = new char[size - i];       //System.arraycopy(num, i, printNum, 0, size - i);//复制数组
            if(i == size)//不打印全0
                return;
            char[] printNum = Arrays.copyOfRange(num, i, size);//复制数组
            System.out.println(printNum);
        }
    
        /**
         *方法二：
         */
    
        /**字符每一位进行全排列   *      * @param n     */
        public void printToMax2(int n){
            if(n <= 0)
                return;
            char[] number = new char[n];
            Arrays.fill(number, '0');
            printOrder(number,n,0);    }
    
        public void printOrder(char[] number, int n, int loc){
            if(loc == n) return;
            for(int i = 0; i <= 9; i++){
                number[loc] = (char)('0' + i);
                if(loc == n - 1){
                    printNumber(number);
                }
                printOrder(number,n,loc + 1);
            }
        }
    }