poj 2250 Compromise(区间dp)

题目链接：http://poj.org/problem?id=2250

思路分析：最长公共子序列问题的变形，只是把字符变成了字符串，按照最长公共子序列的思路即可以求解。

代码如下：

#include <stdio.h>
#include <string.h>

#define IsEqual(a, b) strcmp((a), (b)) == 0
enum { Left, Up, UpAndLeft };
int XLen, YLen;
const int MAX_N =  + ;
char X[MAX_N][], Y[MAX_N][];
int dp[MAX_N][MAX_N], r[MAX_N][MAX_N];

void PrintWords(int i, int j)
{
    if (i ==  || j == )
        return;

    if (r[i][j] == UpAndLeft)
    {
        PrintWords(i - , j - );

        if (i == XLen && j == YLen)
            printf("%s",X[i]);
        else
            printf("%s ", X[i]);
    }
    else
    if (r[i][j] == Up)
        PrintWords(i - , j);
    else
        PrintWords(i, j - );
}

void Lcs( int XLen, int YLen )
{
    for (int i = ; i <= XLen; ++i)
        dp[i][] = ;
    for (int j = ; j <= YLen; ++j)
        dp[][j] = ;

    for (int i = ; i <= XLen; ++i)
        for (int j = ; j <= YLen; ++j)
        {
            if (IsEqual(X[i], Y[j]))
            {
                dp[i][j] = dp[i - ][j - ] + ;
                r[i][j] = UpAndLeft;
            }
            else
            if (dp[i - ][j] >= dp[i][j - ])
            {
                dp[i][j] = dp[i - ][j];
                r[i][j] = Up;
            }
            else
            {
                dp[i][j] = dp[i][j - ];
                r[i][j] = Left;
            }
        }
}

int main()
{
    XLen = YLen = ;

    while (scanf("%s", X[XLen]) != EOF)
    {
        memset(dp, , sizeof(dp));
        memset(r, -, sizeof(r));

        while ()
        {
            scanf("%s", X[++XLen]);
            if (strcmp("#", X[XLen]) == )
            {
                XLen--;
                break;
            }
        }

        while ()
        {
            scanf("%s", Y[YLen++]);
            if (strcmp("#", Y[YLen - ]) == )
            {
                YLen -= ;
                break;
            }
        }

        Lcs(XLen, YLen);
        PrintWords(XLen, YLen);
        printf("\n");
        XLen = YLen = ;
    }

    return ;
}