Create execution-of-all-suffix-instructions-staying-in-a-grid.cpp

Author: kamyu104

C++/execution-of-all-suffix-instructions-staying-in-a-grid.cpp

@@ -0,0 +1,44 @@
+// Time:  O(m)
+// Space: O(m)
+
+class Solution {
+public:
+    vector<int> executeInstructions(int n, vector<int>& startPos, string s) {
+        static const unordered_map<char, pair<int, int>> directions = {
+            {'U', {-1, 0}}, {'R', {0, 1}}, {'D', {1, 0}}, {'L', {0, -1}}
+        };
+
+        int x0 = startPos[0], y0 = startPos[1];
+        int x = 0, y = 0;
+        vector<int> result(size(s));
+        iota(rbegin(result), rend(result), 1);
+        unordered_map<int, vector<int>> lookup_x, lookup_y;
+        lookup_x[x0 - x].emplace_back(0);
+        lookup_y[y0 - y].emplace_back(0);
+        for (int i = 0; i < size(s); ++i) {
+            const auto& [dx, dy] = directions.at(s[i]);
+            x += dx, y += dy;
+            for (const auto& k : {n - x, -x - 1}) {
+                if (!lookup_x.count(k)) {
+                    continue;
+                }
+                for (const auto& j : lookup_x[k]) {
+                    result[j] = min(result[j], i - j);
+                }
+                lookup_x.erase(k);
+            }
+            for (const auto& k : {n - y, -y - 1}) {
+                if (!lookup_y.count(k)) {
+                    continue;
+                }
+                for (const auto& j : lookup_y[k]) {
+                    result[j] = min(result[j], i - j);
+                }
+                lookup_y.erase(k);
+            }
+            lookup_x[x0 - x].emplace_back(i + 1);
+            lookup_y[y0 - y].emplace_back(i + 1);
+        }
+        return result;
+    }
+};