Create shortest-common-supersequence.cpp

Author: kamyu104

C++/shortest-common-supersequence.cpp

@@ -0,0 +1,45 @@
+// Time:  O(m * n)
+// Space: O(m * n)
+
+class Solution {
+public:
+    string shortestCommonSupersequence(string str1, string str2) {
+        vector<vector<int>> dp(2, vector<int>(str2.size() + 1));
+        vector<vector<tuple<int, int, char>>> bt(str1.size() + 1,
+                                                 vector<tuple<int, int, char>>(str2.size() + 1));
+        for (int i = 0; i < str1.length(); ++i) {
+            bt[i + 1][0] = {i, 0, str1[i]};
+        }
+        for (int j = 0; j < str2.length(); ++j) {
+            bt[0][j + 1] = {0, j, str2[j]};
+        }
+        for (int i = 0; i < str1.length(); ++i) {
+            for (int j = 0; j < str2.length(); ++j) {
+                if (dp[i % 2][j + 1] > dp[(i + 1) % 2][j]) {
+                    dp[(i + 1) % 2][j + 1] = dp[i % 2][j + 1];
+                    bt[i + 1][j + 1] = {i, j + 1, str1[i]};
+                } else {
+                    dp[(i + 1) % 2][j + 1] = dp[(i + 1) % 2][j];
+                    bt[i + 1][j + 1] = {i + 1, j, str2[j]};
+                }
+                if (str1[i] != str2[j]) {
+                    continue;
+                }
+                if (dp[i % 2][j] + 1 > dp[(i + 1) % 2][j + 1]) {
+                    dp[(i + 1) % 2][j + 1] = dp[i % 2][j] + 1;
+                    bt[i + 1][j + 1] = {i, j, str1[i]};
+                }
+            }
+        }
+        
+        int i = str1.length(), j = str2.length();
+        char c = 0;
+        string result;
+        while (i != 0 || j != 0) {
+            tie(i, j, c) = bt[i][j];
+            result.push_back(c);
+        }
+        reverse(result.begin(), result.end());
+        return result;
+    }
+};