ONE EDIT DISTANCE | TRICKY | OA PROBLEM | MUST DO

https://www.lintcode.com/problem/640/description

Given two strings S and T, determine if they are both one edit distance apart.
One ediit distance means doing one of these operation:

insert one character in any position of S
delete one character in S
change any one character in S to other character
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Example

Example 1:
Input: s = "aDb", t = "adb"
Output: true
Example 2:

Input: s = "ab", t = "ab"
Output: false
Explanation:
s=t ,so they aren't one edit distance apart

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class Solution {
public:
    bool isOneEditDistance(string s, string t) {
        int m=s.size();
        int n=t.size();
        if(abs(m-n)>1){
            return false;
        }
        for(int i=0;i<min(m,n);i++){
            if(s[i]==t[i]){
                continue;
            }
            bool REPLACE=s.substr(i+1) == t.substr(i+1);
            bool DELETE=s.substr(i+1) == t.substr(i);
            bool INSERT=s.substr(i) == t.substr(i+1); // eg s=bcde , t=abcde
            return REPLACE || DELETE | INSERT;
        }
        return abs(n-m)==1;  // example s=a , t=ab
    }
};