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Author: Jerusus

18.java

@@ -0,0 +1,69 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
+
+class Solution {
+  public List<List<Integer>> fourSum(int[] nums, int target) {
+    Set<List<Integer>> res = new HashSet<>();
+    Arrays.sort(nums);
+    Map<Integer, List<Bi>> map = new TreeMap<>();
+    for (int i = 0; i < nums.length - 1; i++) {
+      for (int j = i + 1; j < nums.length; j++) {
+        int sum = nums[i] + nums[j];
+        Bi b = new Bi(i, j);
+        if (map.containsKey(sum)) {
+          map.get(sum).add(b);
+        } else {
+          List<Bi> a = new ArrayList<>();
+          a.add(b);
+          map.put(sum, a);
+        }
+      }
+    }
+
+    // go up to half of the target
+    for (int a : map.keySet()) {
+      if (a > target / 2) {
+        break;
+      }
+      int b = target - a;
+      if (map.containsKey(b)) {
+        List<Bi> indices_a = map.get(a);
+        List<Bi> indices_b = map.get(b);
+        for (Bi aa : indices_a) {
+          for (Bi bb : indices_b) {
+            if (!aa.con(bb)) {
+              List<Integer> hit = new ArrayList<>();
+              hit.add(nums[aa.a]);
+              hit.add(nums[aa.b]);
+              hit.add(nums[bb.a]);
+              hit.add(nums[bb.b]);
+              Collections.sort(hit);
+              res.add(hit);
+            }
+          }
+        }
+      }
+    }
+    return new ArrayList<>(res);
+  }
+}
+
+class Bi {
+  int a;
+  int b;
+
+  Bi(int a, int b) {
+    this.a = a;
+    this.b = b;
+  }
+
+  public boolean con(Bi o) {
+    return this.a == o.a || this.a == o.b || this.b == o.a || this.b == o.b;
+  }
+}

927.java

@@ -0,0 +1,56 @@
+import java.util.Arrays;
+
+class Solution927 {
+  public static void main(String args[]) {
+    Solution927 s = new Solution927();
+    int[] arr = new int[] { 1, 0, 1, 0, 1 };
+    s.threeEqualParts(arr);
+  }
+
+  public int[] threeEqualParts(int[] arr) {
+    String s = Arrays.toString(arr).replaceAll("\\[|\\]|,|\\s", "");
+    if (!s.contains("1"))
+      return new int[] { 0, 2 };
+    String aa = s.substring(0, 1);
+    String bb = s.substring(1, s.length() - 1);
+    String cc = s.substring(s.length() - 1);
+    String a = trm(aa);
+    String b = trm(bb);
+    String c = trm(cc);
+    while (comp(b, a) >= 0 && comp(b, c) >= 0) {
+      if (comp(a, b) == 0 && comp(b, c) == 0) {
+        return new int[] { aa.length() - 1, aa.length() + bb.length() };
+      }
+      if (comp(c, a) <= 0) {
+        cc = bb.charAt(bb.length() - 1) + cc;
+        bb = bb.substring(0, bb.length() - 1);
+      } else {
+        aa = aa + bb.charAt(0);
+        bb = bb.substring(1);
+      }
+      a = trm(aa);
+      b = trm(bb);
+      c = trm(cc);
+    }
+
+    return new int[] { -1, -1 };
+  }
+
+  String trm(String s) {
+    if (s.indexOf("1") >= 0) {
+      return s.substring(s.indexOf("1"));
+    } else {
+      return "0";
+    }
+  }
+
+  int comp(String s, String o) {
+    if (s.length() > o.length()) {
+      return 1;
+    } else if (o.length() > s.length()) {
+      return -1;
+    }
+
+    return s.compareTo(o);
+  }
+}