HackerRank

HackerRank - common-child【DP】

题意
给出两串长度相等的字符串，找出他们的最长公共子序列e

思路
字符串版的LCS

AC代码

#include <iostream>  
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <deque>
#include <vector>
#include <queue>
#include <string>
#include <cstring>
#include <map>
#include <stack>
#include <set>
#include <cstdlib>
#include <ctype.h>
#include <numeric>
#include <sstream>
using namespace std;

typedef long long LL;
const double PI  = 3.14159265358979323846264338327;
const double E   = 2.718281828459;  
const double eps = 1e-6;
const int MAXN   = 0x3f3f3f3f;
const int MINN   = 0xc0c0c0c0;
const int maxn   = 1e3 * 5 + 5; 
const int MOD    = 1e9 + 7;
int dp[maxn][maxn];

int main()
{
    string a, b;
    cin >> a >> b;
    int i, j;
    int len = a.size();
    memset(dp, 0, sizeof(dp));
    for (i = 0; i < len; i++)
    {
        if (i)
        {
            dp[0][i] = dp[0][i - 1];
            dp[i][0] = dp[i - 1][0];
        }
        if (a[0] == b[i])
            dp[0][i] = 1;
        if (b[0] == a[i])
            dp[i][0] = 1;
    }
    for (i = 1; i < len; i++)
    {
        for (j = 1; j < len; j++)
        {
            if (a[i] == b[j])
                dp[i][j] = dp[i - 1][j - 1] + 1;
            else
                dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
        }
    }
    cout << dp[len - 1][len - 1] << endl;
}