LeetCode 669

Author: LjyYano

solution/0600-0699/0679.24 Game/Solution.java

@@ -0,0 +1,69 @@
+class Solution {
+    public boolean judgePoint24(int[] nums) {
+        return dfs(Arrays.stream(nums).boxed().map(Double::new).collect(Collectors.toList()));
+    }
+
+    private boolean dfs(List<Double> numList) {
+        if (numList.size() == 0) {
+            return false;
+        }
+        if (numList.size() == 1) {
+            return Math.abs(Math.abs(numList.get(0) - 24.0)) < 0.000001d;
+        }
+        for (int i = 0; i < numList.size(); i++) {
+            for (int j = i + 1; j < numList.size(); j++) {
+                boolean valid = dfs(getList(numList, i, j, 0)) || dfs(getList(numList, i, j, 1))
+                        || dfs(getList(numList, i, j, 2)) || dfs(getList(numList, i, j, 3))
+                        || dfs(getList(numList, i, j, 4)) || dfs(getList(numList, i, j, 5));
+                if (valid) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    private List<Double> getList(List<Double> numList, int i, int j, int operate) {
+        List<Double> candidate = new ArrayList<>();
+        for (int k = 0; k < numList.size(); k++) {
+            if (k == i || k == j) {
+                continue;
+            }
+            candidate.add(numList.get(k));
+        }
+
+        switch (operate) {
+            // a + b
+            case 0:
+                candidate.add(numList.get(i) + numList.get(j));
+                break;
+            // a - b
+            case 1:
+                candidate.add(numList.get(i) - numList.get(j));
+                break;
+            // b - a
+            case 2:
+                candidate.add(numList.get(j) - numList.get(i));
+                break;
+            // a * b
+            case 3:
+                candidate.add(numList.get(i) * numList.get(j));
+                break;
+            // a / b
+            case 4:
+                if (numList.get(j) == 0) {
+                    return Collections.emptyList();
+                }
+                candidate.add(numList.get(i) / numList.get(j));
+                break;
+            // b / a
+            case 5:
+                if (numList.get(i) == 0) {
+                    return Collections.emptyList();
+                }
+                candidate.add(numList.get(j) / numList.get(i));
+                break;
+        }
+        return candidate;
+    }
+}