【LeetCode】Plus One && 【九度】题目1198：a+b
Plus One
Total Accepted: 4206 Total Submissions: 14127 My Submissions
Given a number represented as an array of digits, plus one to the number.
题目意思为给定一个数组，这个数组内的数代表某个大数，也就是可能为100位甚至多少位的一个数。
例如123456789012345678901234567890000，那么digits的每个位必然为一个个位数。
两个大数相加，可以使用数组，按位累加。
大于10就进位，同时将当前位-1，并且上一位加1。
Java AC
public class Solution {
public int[] plusOne(int[] digits) {
int len = digits.length;
int addNum[] = new int[len + 1];
addNum[len] = 1;
for (int i = len - 1; i >= 0; i--) {
addNum[i + 1] += digits[i];
if (addNum[i + 1] >= 10) {
addNum[i + 1] -= 10;
addNum[i] += 1;
}
}
if (addNum[0] == 0) {
System.arraycopy(addNum, 1, digits, 0, len);
return digits;
}else {
return addNum;
}
}
}
LeetCode Add Binary 也是大数相加，只不过这次是二进制，知道进制相加的原则即可。
Java AC
public class Solution {
public String addBinary(String a, String b) {
if(a == null || b == null){
return "";
}
if("".equals(a) || "".equals(b)){
return "";
}
if("".equals(a.replaceAll("0", "")) && "".equals(b.replaceAll("0", ""))){
return "0";
}
int len1 = a.length();
int len2 = b.length();
char arrayA[] = a.toCharArray();
char arrayB[] = b.toCharArray();
int maxLen = Math.max(len1,len2);
int minLen = Math.min(len1,len2);
int array[] = new int[maxLen+1];
int k = maxLen;
if(maxLen == len1){
for(int i = minLen-1; i >= 0; i--){
array[k] += arrayA[k-1] - '0' + arrayB[i] - '0';
if(array[k] >= 2){
array[k] -= 2;
array[k-1] += 1;
}
k--;
}
while(k > 0){
array[k] += arrayA[k-1] - '0';
if(array[k] >= 2){
array[k] -= 2;
array[k-1] += 1;
}
k--;
}
}else{
for(int i = minLen-1; i >= 0; i--){
array[k] += arrayA[i] - '0' + arrayB[k-1] - '0';
if(array[k] >= 2){
array[k] -= 2;
array[k-1] += 1;
}
k--;
}
while(k > 0){
array[k] += arrayB[k-1] - '0';
if(array[k] >= 2){
array[k] -= 2;
array[k-1] += 1;
}
k--;
}
}
StringBuffer sb = new StringBuffer();
int i = 0;
if(array[0] == 0){
i = 1;
}
for(; i < maxLen+1; i++){
sb.append(array[i]);
}
return sb.toString();
}
}
九度题目1198：a+b 2010年华中科技大学计算机研究生机试真题是一类题。
当时用了三种解法去解决。
一并给代码。
方法1 Java AC
import java.math.BigDecimal;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()){
String a = scanner.next();
String b = scanner.next();
BigDecimal ad = new BigDecimal(a);
BigDecimal bd = new BigDecimal(b);
BigDecimal c = ad.add(bd);
System.out.println(c);
}
}
}
/**************************************************************
Problem: 1198
User: wzqwsrf
Language: Java
Result: Accepted
Time:980 ms
Memory:84752 kb
****************************************************************/
方法2 Java AC
import java.util.Scanner;
public class Main {
/*
* 1198
*/
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()){
String a = scanner.next();
String b = scanner.next();
int alength = a.length();
int blength = b.length();
int minlength = Math.min(alength, blength);
int maxlength = Math.max(alength, blength);
int in = 0 ;
String result = "";
String maxStr = alength>blength?a:b;
String minStr = alength<blength?a:b;
int c = maxlength-minlength;
for (int i = minlength -1; i >= 0; i--) {
int sa = minStr.charAt(i)-'0';
int sb = maxStr.charAt(c + i)-'0';
int count = sa+sb+in;
if(count >= 10){
in = 1;
result = count-10+result;
}else{
in = 0 ;
result = count + result;
}
}
for (int i = c-1 ; i >= 0 ; i--) {
int max = maxStr.charAt(i)-'0';
int count = max+in;
if(count>=10){
in = 1;
result = count-10+result;
}else{
in = 0 ;
result = count + result;
}
}
if(in==1){
result = in +result ;
}
System.out.println(result);
}
}
}
/**************************************************************
Problem: 1198
User: wzqwsrf
Language: Java
Result: Accepted
Time:1120 ms
Memory:210296 kb
****************************************************************/
方法3 Java AC
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()){
String a = scanner.next();
String b = scanner.next();
int aLength = a.length();
int bLength = b.length();
int max = Math.max(aLength, bLength);
int[] arrayA = new int[max+1];
int[] arrayB = new int[max+1];
int k = 0;
for (int i = max+1-aLength ; i< max+1; i++ ) {
arrayA[i] = a.charAt(k)-'0';
k++;
}
k = 0;
for (int i = max+1-bLength ; i< max+1; i++ ) {
arrayB[i] = b.charAt(k)-'0';
k++;
}
int[] arrayC = new int[max+1];
for (int i = max ; i> 0 ;i--) {
arrayC[i] += arrayA[i] + arrayB[i];
if (arrayC[i]>=10) {
arrayC[i] -= 10;
arrayC[i-1] += 1;
}
}
if (arrayC[0] == 0) {
for (int i = 1; i < arrayC.length; i++) {
System.out.print(arrayC[i]);
}
System.out.println();
}else {
for (int i = 0; i < arrayC.length; i++) {
System.out.print(arrayC[i]);
}
System.out.println();
}
}
}
}
/**************************************************************
Problem: 1198
User: wzqwsrf
Language: Java
Result: Accepted
Time:2290 ms
Memory:95360 kb
****************************************************************/