leetcode 66. Plus One （大整数加一）

本文链接：https://blog.youkuaiyun.com/m0_37795244/article/details/108092691

本文介绍了一种在给定的非空数字数组上进行加一操作的算法，该数组表示一个非负整数。文章提供了C++、Java、Python和Go四种语言的实现代码，展示了如何遍历数组，从最低位开始逐位加一并处理进位，最终返回加一后的数字数组。

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Given a non-empty array of digits representing a non-negative integer, increment one to the integer.

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contains a single digit.

You may assume the integer does not contain any leading zero, except the number 0 itself.

Example 1:

Input: [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.
Example 2:

Input: [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

很简单，直接操作

C++

class Solution {
public:
    vector<int> plusOne(vector<int>& a) {
        int n=a.size();
        a[n-1]+=1;
        int up=0;
        for(int i=n-1;i>=0;i--){
            int tmp=a[i]+up;
            a[i]=tmp%10;
            up=tmp/10;
        }
        if(up)a.insert(a.begin(),1);
        return a;
    }
};

Java

还有一种 early return 的做法，很棒

class Solution {
    public int[] plusOne(int[] a) {
        int n=a.length;
        int up=0;
        for(int i=n-1;i>=0;i--){
            if(a[i]<9){
                a[i]++;
                return a;
            }
            a[i]=0;
        }
        int[] res=new int[n+1];
        res[0]=1;
        return res;
    }
}

Python

class Solution:
    def plusOne(self, a: List[int]) -> List[int]:
        n=len(a)
        for i in range(n-1,-1,-1):
            if a[i]<9 :
                a[i]+=1
                return a
            a[i]=0
        a.insert(0,1)
        return a

Go

func plusOne(a []int) []int {
    n:=len(a)
    for i:=n-1;i>=0;i-- {
        if a[i]<9 {
            a[i]++
            return a
        }
        a[i]=0
    }
    r:=make([]int, n+1)
    r[0]=1
    return r
}

另一种写法

func plusOne(a []int) []int {
    n,up:=len(a),1
    for i:=n-1;i>=0;i-- {
        tmp:=a[i]+up
        a[i],up=tmp%10,tmp/10
    }
    if up!=0 {
        return append([]int{up}, a...)
    }
    return a
}