Create shortest-distance-to-target-color.cpp

Author: kamyu104

C++/shortest-distance-to-target-color.cpp

@@ -0,0 +1,73 @@
+// Time:  O(n)
+// Space: O(n)
+
+class Solution {
+public:
+    vector<int> shortestDistanceColor(vector<int>& colors, vector<vector<int>>& queries) {   
+        vector<vector<int>> dp(3, vector<int>(colors.size(), numeric_limits<int>::max()));
+        dp[colors[0] - 1][0] = 0;
+        for (int i = 1; i < colors.size(); ++i) {
+            for (int color = 0; color < 3; ++color) {
+                if (dp[color][i - 1] != numeric_limits<int>::max()) {
+                    dp[color][i] = dp[color][i - 1] + 1;
+                }
+            }
+            dp[colors[i] - 1][i] = 0;
+        }
+
+        dp[colors[colors.size() - 1] - 1][colors.size() - 1] = 0;
+        for (int i = colors.size() - 2; i >= 0; --i) {
+            for (int color = 0; color < 3; ++color) {
+                if (dp[color][i + 1] != numeric_limits<int>::max()) {
+                    if (abs(dp[color][i + 1] - 1) < dp[color][i]) {
+                        dp[color][i] = dp[color][i + 1] - 1;
+                    }
+                }
+            }
+            dp[colors[i] - 1][i] = 0;
+        }
+
+        vector<int> result;
+        for (const auto& query : queries) {
+            const auto d = abs(dp[query[1] - 1][query[0]]);
+            result.emplace_back(d != numeric_limits<int>::max() ? d : -1);
+        }
+        return result;
+    }
+};
+
+// Time:  O(n)
+// Space: O(n)
+class Solution2 {
+public:
+    vector<int> shortestDistanceColor(vector<int>& colors, vector<vector<int>>& queries) {   
+        vector<vector<int>> left(3, vector<int>(colors.size(), numeric_limits<int>::max()));
+        left[colors[0] - 1][0] = 0;
+        for (int i = 1; i < colors.size(); ++i) {
+            for (int color = 0; color < 3; ++color) {
+                if (left[color][i - 1] != numeric_limits<int>::max()) {
+                    left[color][i] = left[color][i - 1] + 1;
+                }
+            }
+            left[colors[i] - 1][i] = 0;
+        }
+
+        vector<vector<int>> right(3, vector<int>(colors.size(), numeric_limits<int>::max()));
+        right[colors[colors.size() - 1] - 1][colors.size() - 1] = 0;
+        for (int i = colors.size() - 2; i >= 0; --i) {
+            for (int color = 0; color < 3; ++color) {
+                if (right[color][i + 1] != numeric_limits<int>::max()) {
+                    right[color][i] = right[color][i + 1] + 1;
+                }
+            }
+            right[colors[i] - 1][i] = 0;
+        }
+
+        vector<int> result;
+        for (const auto& query : queries) {
+            const auto d = min(left[query[1] - 1][query[0]], right[query[1] - 1][query[0]]);
+            result.emplace_back(d != numeric_limits<int>::max() ? d : -1);
+        }
+        return result;
+    }
+};