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  • hoj1227 Common Subsequence

    LCS最长公共子序列模板:

    状态转移方程为
    dp[i][j]=dp[i-1][j-1]+1 if(in[i]==target[i])
    =max{dp[i-1][j],dp[i][j-1]} else;
    void LCSLength(int m,int n,char *x,char *y,int **c,int **b)
    {
    int i,j;
    for (i = 1; i <= m; i++) c[i][0] = 0;
    for (i = 1; i <= n; i++) c[0][i] = 0;
    for (i = 1; i <= m; i++)
    for (j = 1; j <= n; j++)
    {
    if (x[i]==y[j]) {
    c[i][j]=c[i-1][j-1]+1; b[i][j]=1;} //b[i][j]用于构造最长公共子序列
    else if (c[i-1][j]>=c[i][j-1]) {
    c[i][j]=c[i-1][j]; b[i][j]=2;}
    else { c[i][j]=c[i][j-1]; b[i][j]=3; }
    }
    }
    法二:
    memset(dp,0,sizeof(dp));
    int len1 = in.size();
    int len2 = target.size();

    for(i=1;i<=len1;i++) //LCS最长子序列
    for(j=1;j<=len2;j++)
    {
    if(in[i-1]==target[j-1])
    dp[i][j]=dp[i-1][j-1]+1;
    else
    dp[i][j] = Max(dp[i-1][j],dp[i][j-1]);
    }
    答案为dp[len1][len2]

    #include <iostream>
    #include <string>
    #include <cstring>
    using namespace std;
    #define X 250
    int dp[X][X]; //不知多大
    int Max(int a,int b)
    {
    return a>b?a:b;
    }
    int main()
    {
    freopen("sum.in","r",stdin);
    freopen("sum.out","w",stdout);
    string in,target;
    int i,j;
    while(cin>>in>>target)
    {
    memset(dp,0,sizeof(dp));
    int len1 = in.size();
    int len2 = target.size();

    for(i=1;i<=len1;i++) //LCS最长公共子序列模板
    for(j=1;j<=len2;j++)
    {
    if(in[i-1]==target[j-1])
    dp[i][j]=dp[i-1][j-1]+1;
    else
    dp[i][j] = Max(dp[i-1][j],dp[i][j-1]);
    }
    cout<<dp[len1][len2]<<endl;
    }
    return 0;
    }

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  • 原文地址:https://www.cnblogs.com/yejinru/p/2374703.html
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