HDU 1159 最长公共子序列

最初写法：

	dp[0][0] = s1[0]==s2[0]?1:0;
	for(int j = 1; j < len2; j++)
	{
    		if(s1[0]==s2[j])
    			dp[0][j] = 1;
   			else
   				dp[0][j] = max(dp[0][j],dp[0][j-1]);
    	}
    	for(int i = 1; i < len1; i++)
    	{
	    	if(s1[i]==s2[0])
    			dp[i][0] = 1;
   			else
   				dp[i][0] = max(dp[i][0],dp[i-1][0]);
	    }
	    for(int i = 1; i < len1; i++)   //***********
	    {
	        for(int j = 1; j < len2; 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]);
            }

最后的：

       int len1 = strlen(s1),len2 = strlen(s2);  
        for(int i = 1; i <= len1; i++)  //***********
        {  
            for(int j = 1; j <= len2; j++)  //*********
            {  
                if(s1[i-1]==s2[j-1])  
                    dp[i][j] = dp[i-1][j-1]+1;  
                else  
                    dp[i][j] = max(dp[i-1][j],dp[i][j-1]);  
            }  
        }

另一种写法：

       for(int i = len1-1; i >= 0; i--)  //**********
        {  
            for(int j = len2-1; j >= 0; 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[0][0]<<endl;  

完整代码：

#include <iostream>  
#include <cstdio>  
#include <cstring>  
#include <algorithm>  
#include <cmath>  
#include <string>  
#include <iomanip>  
using namespace std;  
#define maxn 1005  
int max(int a, int b)  
{  
    return a>b?a:b;  
}  
char s1[maxn],s2[maxn];  
int dp[maxn][maxn];  
int main(int argc, char *argv[])  
{  
    while(scanf("%s %s",s1,s2)!=EOF)  
    {  
        cin.get();  
        int len1 = strlen(s1),len2 = strlen(s2);  
        for(int i = 0; i <= len1; i++)  
                dp[i][0] = 0;  
            for(int j = 0; j <= len2; j++)  
                dp[0][j] = 0;   
  
        for(int i = 1; i <= len1; i++)  
        {  
            for(int j = 1; j <= len2; j++)  
            {  
                if(s1[i-1]==s2[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;  
}