Create minimum-ascii-delete-sum-for-two-strings.cpp

Author: kamyu104

Diff for: C++/minimum-ascii-delete-sum-for-two-strings.cpp

@@ -0,0 +1,55 @@
+// Time:  O(m * n)
+// Space: O(n)
+
+// DP with rolling window.
+class Solution {
+public:
+    int minimumDeleteSum(string s1, string s2) {
+        vector<vector<int>> dp(2, vector<int>(s2.length() + 1));
+        for (int j = 0; j < s2.length(); ++j) {
+            dp[0][j + 1] = dp[0][j] + s2[j];
+        }
+
+        for (int i = 0; i < s1.length(); ++i) {
+            dp[(i + 1) % 2][0] = dp[i % 2][0] + s1[i];
+            for (int j = 0; j < s2.length(); ++j) {
+                if (s1[i] == s2[j]) {
+                    dp[(i + 1) % 2][j + 1] = dp[i % 2][j];
+                } else {
+                    dp[(i + 1) % 2][j + 1] = min(dp[i % 2][j + 1] + s1[i],
+                                                 dp[(i + 1) % 2][j] + s2[j]);
+                }
+            }
+        }
+
+        return dp[s1.length() % 2][s2.length()];
+    }
+};
+
+// Time:  O(m * n)
+// Space: O(m * n)
+class Solution2 {
+public:
+    int minimumDeleteSum(string s1, string s2) {
+        vector<vector<int>> dp(s1.length() + 1, vector<int>(s2.length() + 1));
+        for (int i = 0; i < s1.length(); ++i) {
+            dp[i + 1][0] = dp[i][0] + s1[i];
+        }
+        for (int j = 0; j < s2.length(); ++j) {
+            dp[0][j + 1] = dp[0][j] + s2[j];
+        }
+
+        for (int i = 0; i < s1.length(); ++i) {
+            for (int j = 0; j < s2.length(); ++j) {
+                if (s1[i] == s2[j]) {
+                    dp[i + 1][j + 1] = dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = min(dp[i][j + 1] + s1[i],
+                                           dp[i + 1][j] + s2[j]);
+                }
+            }
+        }
+
+        return dp[s1.length()][s2.length()];
+    }
+};