Math start!

(1) ADD Digits

Problem Solving Ideas:

A mathematical attribute based on congruence. The root of the number (that is, the final result required to be returned by the topic) is the same as the remainder of the number divided by 9 (and the remainder will always be a single number).

Take 438 as an example

[Step 1]:

438  == 40*10 +3*10 +8 ;4+3+8 == 4*(10%9)*(10%9)+3*(10%9)+8%9= 15 ;

[Step 2]:

15  == 1*10 + 5 ; 1+5 == 1*(10%9)+5%9= 6 ;

[So we can see]:

return num%9; and don‘t forget num==0 or num==9   

The code is as follows:

1  Public class Solution {2      Public  int adddigits (int  num) {3         return  num = = 0? 0: (num%9 = = 0? 9 : (num%9)); 4     }5 }

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(2) Minimum Moves to Equal Array Elements

Problem Solving Ideas:

To achieve the goal of making the elements in the array equal, add 1 to the n-1 element and subtract 1 from one element. therefore, the best way is to make all the elements in the array equal to the min element. sum (array)-N * Minimum

The code is as follows:

1  Public classSolution {2      Public intMinmoves (int[] nums) {3         if(Nums.length = = 0) {4             return0;5         }6         intMin = nums[0];7         intsum = 0;8          for(intn:nums) {9Min =math.min (n, min);TenSum + =N; One         } A         returnsum-nums.length*min; -     } -}

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(3) Excel Sheet Column Title

Problem Solving Ideas:

The essence is to convert the number of 10 into 26 binary.

The code is as follows:

1  Public class Solution {2      Public String converttotitle (int  n) {3         return n = = 0? "": Converttotitle (--N/26) + (char) (' A ' + (n%)); 4         // return n = = 0? "": Converttotitle ((n-1)/+) + (char) (' A ' + ((n-1)%)); 5     }6 }

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Math start!