POJ 1458 Common Subsequence

Description
A subsequence of a given sequence is the given sequence with some elements (possible none) left out. Given a sequence X = < x1, x2, …, xm > another sequence Z = < z1, z2, …, zk > is a subsequence of X if there exists a strictly increasing sequence < i1, i2, …, ik > of indices of X such that for all j = 1,2,…,k, xij = zj. For example, Z = < a, b, f, c > is a subsequence of X = < a, b, c, f, b, c > with index sequence < 1, 2, 4, 6 >. Given two sequences X and Y the problem is to find the length of the maximum-length common subsequence of X and Y.

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【题目分析】
沉迷水题无法自拔。
求最长公共子序列问题，只需要n^2转移一下就可以了。（方程见代码）

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【代码】

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
char s1[1001],s2[1001];
int dp[1001][1001];
int main()
{
    while (~scanf("%s%s",s1+1,s2+1))
    {
        memset(dp,0,sizeof dp);
        int l1=strlen(s1+1),l2=strlen(s2+1);
        for (int i=1;i<=l1;++i)
            for (int j=1;j<=l2;++j)
                if (s1[i]==s2[j]) dp[i][j]=dp[i-1][j-1]+1;
                else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        cout<<dp[l1][l2]<<endl;
    }
}