Solidity如何通过代码减少gas消耗

pragma solidity ^0.5.10;

contract Test{
    
    struct User{
        uint age;
        uint balance;
        uint num;
    }
    
    User user;
    
    function initUser() public{
        user = User({age:20,balance:1000,num:1});
    }
    
    function setUser1() public {
        user.age = 30;
        user.balance = 20000;
        user.num = 2;
    }
    
    function setUser2() public {
        User memory temp = user;
        temp.age = 40;
        temp.age = 20001;
        user.num = 3;
        user = temp;
    }
}