标签：image while space div class 回溯 char names 技术分享
不知道最后怎么输出，因为公共部分只输出一次。有人说回溯输出，感觉好巧妙！其实就是下图，输出的就是那条灰色的路径，但是初始时边界一定要初始化一下，因为最第一列只能向上走，第一行只能向左走。我用1表示向上走，2向左上方走，3向左走。
刚开始输入字符串时有两种方法，直接输入；或从地址后一位输入，即此时数组起始编号为1。直接输入时，dp[i][j]表示的是以s1[i-1],s2[j-1]为结尾LCS，另一种则就是表示以s1[i],s2[j]为结尾的LCS。两者在路径输出时有些差别，以前感觉直接输出LCS长度后者方便，其实都一样。
1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 using namespace std; 6 const int MAXN = 107; 7 char s1[MAXN], s2[MAXN]; 8 int dp[MAXN][MAXN], flag[MAXN][MAXN]; 9 int len1, len2; 10 11 void LCS() 12 { 13 memset(dp, 0, sizeof(dp)); 14 for (int i = 0; i <= len1; i++) flag[i][0] = 1; 15 for (int i = 0; i <= len2; i++) flag[0][i] = 3; 16 for (int i = 1; i <= len1; i++) { 17 for (int j = 1; j <= len2; j++) { 18 if (s1[i - 1] == s2[j - 1]) { 19 dp[i][j] = dp[i - 1][j - 1] + 1; 20 flag[i][j] = 2; 21 } 22 else if (dp[i - 1][j] >= dp[i][j - 1]) { 23 dp[i][j] = dp[i - 1][j]; 24 flag[i][j] = 1; 25 } 26 else { 27 dp[i][j] = dp[i][j - 1], flag[i][j] = 3; 28 } 29 } 30 } 31 } 32 33 void Print(int x, int y) 34 { 35 if (x == 0 && y == 0) return; 36 if (flag[x][y] == 2) { 37 Print(x - 1, y - 1); 38 cout << s1[x-1]; 39 } 40 else if (flag[x][y] == 1) { 41 Print(x - 1, y); 42 cout << s1[x - 1]; 43 } 44 else { 45 Print(x, y - 1); 46 cout << s2[y - 1]; 47 } 48 } 49 50 int main() 51 { 52 while (cin>>s1>>s2) 53 { 54 len1 = strlen(s1), len2 = strlen(s2); 55 LCS(); 56 Print(len1, len2); 57 cout << endl; 58 } 59 return 0; 60 }
起始编号为1：
1 #include<cstdio> 2 #include<cstring> 3 #include<iostream> 4 using namespace std; 5 const int MAXN = 107; 6 int dp[MAXN][MAXN], flag[MAXN][MAXN]; 7 char s1[MAXN], s2[MAXN]; 8 int len1, len2; 9 10 void LCS() 11 { 12 for (int i = 0; i <= len1; i++) flag[i][0] = 1; 13 for(int i = 0; i <= len2; i++) flag[0][i] = 3; 14 for (int i = 1; i <= len1; i++) { 15 for (int j = 1; j <= len2; j++) { 16 if (s1[i] == s2[j]) 17 dp[i][j] = dp[i - 1][j - 1] + 1, flag[i][j] = 2; 18 else if (dp[i - 1][j] >= dp[i][j - 1]) 19 dp[i][j] = dp[i - 1][j], flag[i][j] = 1; 20 else dp[i][j] = dp[i][j - 1], flag[i][j] = 3; 21 } 22 } 23 } 24 25 void Print(int x, int y) 26 { 27 if (x == 0 && y == 0) return; 28 if (flag[x][y] == 2) { 29 Print(x - 1, y - 1); 30 printf("%c", s1[x]); 31 } 32 else if (flag[x][y] == 1) { 33 Print(x - 1, y); 34 printf("%c", s1[x]); 35 } 36 else { 37 Print(x, y - 1); 38 printf("%c", s2[y]); 39 } 40 return; 41 } 42 43 int main() 44 { 45 while (scanf("%s %s", s1 + 1, s2 + 1)==2) 46 { 47 len1 = strlen(s1 + 1), len2 = strlen(s2 + 1); 48 memset(dp, 0, sizeof(dp)); 49 LCS(); 50 Print(len1, len2); 51 printf("\n"); 52 } 53 return 0; 54 }
标签：image while space div class 回溯 char names 技术分享
原文地址：http://www.cnblogs.com/zxhyxiao/p/7436606.html
