Li Kou daily question - day 31 -1790 Can a string exchange be performed only once to make two strings equal

2022.6.30 Did you brush the questions today ？

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subject ：

Give you two strings of equal length s1 and s2 . once String swapping The operation steps are as follows ： Select two subscripts in a string （ It doesn't have to be different ）, And exchange the characters corresponding to the two subscripts .

If the One of the strings perform At most one string exchange You can make two strings equal , return true ; otherwise , return false .

analysis ：

For looking at two strings , By exchanging strings once , Can you make two strings equal .

Ideas ： Traversing one of the strings , When the subscripts are the same but the elements are different , Save these two different elements separately , And then continue to traverse , If something different happens , Then judge whether the elements saved before are the same as those to be exchanged now , The same can be saved , Not the same , And exit directly . If it's the same, continue to judge whether it needs to be exchanged in the future

analysis ：

1. Violent solution

class Solution {
public:
    bool areAlmostEqual(string s1, string s2) {
        char c1='#',c2=c1;
        bool isChange=false;
        int n=s1.size();
        for(int i=0;i<n;i++){
            if(s1[i]!=s2[i]){
                if(isChange)return false;
                else if(c1=='#'){
                    c1=s1[i];
                    c2=s2[i];
                }
                else{
                    if(c1==s2[i]&&c2==s1[i]){
                        isChange=true;
                        c2='#';
                    }
                    else return false;
                }
            }
        }
        // see c2 Is it #
        return c2=='#';
    }
};