1323. Maximum number of 6 and 9

Address ：

Power button https://leetcode-cn.com/problems/maximum-69-number/

subject ：

Give you a number only 6 and 9 Positive integer composed of  num.

You can only flip one digit at most , take 6 become  9, Or the  9 become  6 .

Please return the maximum number you can get .

Example 1：

Input ：num = 9669 Output ：9969 explain ： Change the first digit to get 6669 . Change the second digit to get 9969 . Change the third digit to get 9699 . Change the fourth digit to get 9666 . The biggest number is 9969 .

Example 2：

Input ：num = 9996 Output ：9999 explain ： Take the last one from 6 Change to 9, As a result, 9999 It's the biggest number .

Example 3：

Input ：num = 9999 Output ：9999 explain ： It's the biggest number without change .

Tips ：

1 <= num <= 10^4 num  The number in each digit is 6 perhaps  9 .

source ： Power button （LeetCode）
link ：https://leetcode-cn.com/problems/maximum-69-number
Copyright belongs to the network . For commercial reprint, please contact the official authority , Non-commercial reprint please indicate the source .

Ideas ：

Intuition is to put numbers into an integer array , So each bit represents a carry , Convenient operation

The integer number is traversed in order to get each digit , such as ：

Numbers	%10	/10
1234	4	123
123	3	12
12	2	1
1	1	0

Method 1 、 Integer array save value operation

int maximum69Number (int num){
	int ret = 0;
	int cnum[5];
	memset(cnum, 0, sizeof(cnum));
	
	int i = 0;
	while(num)
	{
		cnum[i++] = num % 10;
		num /= 10;
	}
	
	int clen = i;
	
	for(int j=clen-1; j>=0; j--)
	{
		int ch = cnum[j];
		
		if(ch != 9)
		{
			cnum[j] = 9;
			break;
		}
	}
	
	for(i=clen-1; i>=0; i--)
	{
		ret *= 10;
		ret += cnum[i];
	}
	
	return ret;
}

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