nyoj36-最长公共子序列 （LCS）

#include <fstream>
#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int INF=0x7fffffff;
const int N=1005;
char s1[N],s2[N];
int dp[N][N];

int main()
{
    //freopen("D:\\input.in","r",stdin);
    //freopen("D:\\output.out","w",stdout);
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        scanf("%s %s",s1+1,s2+1);
        int l1=strlen(s1+1);
        int l2=strlen(s2+1);
        dp[0][0]=0;
        dp[1][0]=0;
        dp[0][1]=0;
        for(int i=1;i<=l1;i++){
            for(int j=1;j<=l2;j++){
                if(s1[i]==s2[j]){
                    dp[i][j]=1+dp[i-1][j-1];
                }else{
                    dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
                }
            }
        }
        printf("%d\n",dp[l1][l2]);
    }
    return 0;
}

#include <stdio.h>
#include <string.h>
char s1[1001], s2[1001];
int dp[1001], t, old, tmp;
int main(){
    scanf("%d", &t);
    getchar();
    while(t--){
        gets(s1);
        gets(s2);
        memset(dp, 0, sizeof(dp));
        int lenS1=strlen(s1), lenS2=strlen(s2);
        for(int i=0; i<lenS1; i++){
            old=0;
            //若s1[i]==s2[j], dp[i][j] = dp[i-1][j-1]+1
            //否则，dp[i][j] = max(dp[i-1][j], dp[i][j-1])
            //此处进行了空间优化，old 代表 dp[i-1][j-1]
            //dp[j-1] 代表 dp[i][j-1], dp[j] 代表 dp[i-1][j]
            for(int j=0; j<lenS2; j++){
                tmp = dp[j];
                if(s1[i]==s2[j])
                    dp[j] = old+1;
                else
                    if(dp[j-1]>dp[j])dp[j]=dp[j-1];
                old = tmp;
            }
        }
        printf("%d\n", dp[lenS2-1]);
    }
    return 0;
} 

#include <stdio.h>
#include <cstring>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int n,m;
const int CHAR = 256;
const int maxn = 1010;
int  ans[maxn*maxn];
int  dp[maxn*maxn];
char S[maxn];
vector<int>v[CHAR];

int er(int l,int r,int x)
{
    while(l<=r)
    {
        int mid = (l+r)/2;
        if( ans[mid] >= x ) r = mid - 1;
        else               l = mid + 1;
    }
    return l;
}



int main()
{
    scanf("%d",&n);
    while( n-- )
    {
        for(int i=0 ; i<CHAR ; i++) v[i].clear();

        scanf("%s",S);
        int l = strlen(S);
        for(int i=l-1 ; i>=0 ; i-- )   {
            v[ S[i] ].push_back(i); ///S[i]字符在字符串对应的位置
            ///cout << S[i] << " " << v[ S[i] ].size() << endl;
        }

        int x = 0;
        scanf("%s",S);
        l = strlen(S);
        for(int i=0 ; i<l ; i++ ){
            int k = v[ S[i] ].size();
            if( k )
            {
                for(int j=0 ; j<k ; j++ )
                {
                    dp[x++] = v[ S[i] ][j];
                }
            }
        }

        m = 0;
        ans[m] = -1<<30;
        for(int i=0; i<x ; i++)
        {
            int x = er(0,m,dp[i]);
            ans[x] = dp[i];
            if( x == m+1 ) m++;
        }
        printf("%d\n",m);
    }
    return 0;
}