51Nod 1006 最长公共子序列Lcs

#include<cstring>
#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;

const int maxn = 1010;
char a[maxn], b[maxn];
int f[maxn][maxn];
string s;

int main()
{
    scanf("%s", a + 1);
    scanf("%s", b + 1);
    int n = strlen(a + 1);
    int m = strlen(b + 1);
    for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++)
    {
        if (a[i] == b[j]) f[i][j] = f[i - 1][j - 1] + 1;
        else f[i][j] = max(f[i - 1][j], f[i][j - 1]);
    }
    //动态规划找LCS
    int i = n, j = m;
    while (i && j)
    {
        if (a[i] == b[j])
        {
            s += a[i];
            i--;
            j--;
        }
        else if (f[i][j] == f[i - 1][j]) 
            i--;
        else 
            j--;
    }
    int len = s.length();
    for (int i = len - 1; i >= 0; i--)
        printf("%c", s[i]);
    return 0;
}