Longest common sub-sequence DP

The algorithm teacher's assignment, a DP basic problem, gives you two sequences, asking you what the longest common subsequence is, such as: (A, B) is a subsequence (a,c,d,b). Note that not the longest common substring, where a subsequence can be discontinuous.

Two for loop out, each dp[i][j] can from dp[i-1][j-1], dp[i-1][j], dp[i][j-1] Three kinds of situation update come over, take a maximum, and then the path with 123 to save down, and finally follow the path and then reverse the output line.

Sample input:

7 4
A b C b D A b
b C D b
7 6
A b C b D A b
b D C a B A
8 4
A B C D E F G H
D C B A

#include <iostream> #include <stdio.h> #include <math.h> #include <stdlib.h> #include < string> #include <string.h> #include <algorithm> #include <vector> #include <queue> #include <set> #include <map> #include <stack>using namespace std;typedef long long ll;const int inf=0x7fffffff; const int Max_n=1009;char x[max_n],y[max_n];int m,n,ct;int dp[max_n][max_n];int B[max_n][max_n];char ans[MAX_N];void Solve () {for (int i=1;i<=m;i++) {for (int j=1;j<=n;j++) {if (X[i]==y[j]) {dp[i][j]=                dp[i-1][j-1]+1;            B[i][j]=1;                } else if (Dp[i-1][j]>=dp[i][j-1]) {dp[i][j]=dp[i-1][j];            b[i][j]=2;                } else{Dp[i][j]=dp[i][j-1];            b[i][j]=3; }}}}void go_back (int x,int y) {if (x==0| |    y==0) return;        if (b[x][y]==1) {ans[++ct]=x[x];    Return Go_back (x-1,y-1);    }if (b[x][y]==2) {return go_back (x-1,y);    } if (b[x][y]==3) {return go_back (x,y-1);    }}int Main () {printf ("Enter the length of x and y: \ n");        while (scanf ("%d%d", &m,&n)!=eof) {memset (dp,0,sizeof (DP));        Memset (b,0,sizeof (b));        printf ("Input sequence x:\n");        for (int i=1;i<=m;i++) {scanf ("%c", &x[i]);        }//GetChar ();        printf ("Input sequence y:\n");        for (int i=1;i<=n;i++) {scanf ("%c", &y[i]);        } solve ();        printf ("eldest-oldest sequence length:%d\n", Dp[m][n]);        ct=0;        Go_back (M,n);        printf ("One of the oldest sequences is: \ n");        for (int i=ct;i>=1;i--) {printf ("%c", Ans[i]);    } printf ("The length of the input x and y: \ n"); } return 0;}

Longest common sub-sequence DP