Leetcode 1092. The shortest common supersequence (DAY 69) ---- dynamic programming learning period (first go to the second brush to do the hardest from the back of the sequence)

Original title

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Code implementation (see the solution for the first brush part and self-solve part)

class Solution {
    
    
public:
    string shortestCommonSupersequence(string str1, string str2) {
    
    
        int strl1 = str1.size(),strl2 = str2.size(),i,j;
        string ret,temp;
        vector<vector<string>> dp(strl1+1,vector<string>(strl2+1,""));
        for(i=1;i<=strl1;++i)
        {
    
    
            for(j=1;j<=strl2;++j)
            {
    
    
                if(str1[i-1] != str2[j-1])
                {
    
    
                    if(dp[i-1][j].size() > dp[i][j-1].size())
                        dp[i][j] = dp[i-1][j];
                    else    dp[i][j] = dp[i][j-1];
                }
                else
                    dp[i][j] = dp[i-1][j-1] + str1[i-1];
            }
        }
        temp = dp[strl1][strl2];
        i=j=0;
        for(char ch:temp)
        {
    
    
            while(i<strl1 && str1[i]!=ch)
                ret+=str1[i++];
            while(j<strl2 && str2[j]!=ch)
                ret+=str2[j++];
            ret+=ch;++i,++j;
        }
        return ret+str1.substr(i)+str2.substr(j);
    }
};