1

cache/src/main/java/com/wyl/cache/Solution.java

@@ -49,39 +49,63 @@ class Solution {
 
 
     public static boolean canThreePartsEqualSum(int[] arr) {
-        int sum = Arrays.stream(arr).sum();
+        int sum = 0;
+        for (int a : arr) {
+            sum += a;
+        }
         if (sum % 3 != 0) {
             return false;
         }
         int avg = sum / 3;
-        for (int i = 0; i < arr.length; i++) {
-            int tmp = avg - arr[i];
-            if (tmp > 0) {
-            } else if (tmp == 0) {
-
-                for (int j = i + 1; j < arr.length; j++) {
-                    tmp = avg - arr[i + 1];
-                    tmp = tmp - arr[j];
-                    if (tmp > 0) {
-
-                    }
-                    if (tmp == 0) {
-                        return true;
-                    }
-                    if (tmp < 0) {
-                        return false;
-                    }
-                }
-            } else {
-                return false;
+        sum = avg;
+        int res = 0;
+        int j = 0;
+        while (j < arr.length - 1 && res < 2) {
+            sum -= arr[j];
+            if (sum == 0) {
+                res++;
+                sum = avg;
             }
-
+            j++;
+        }
+        if (res == 2) {
+            return true;
         }
         return false;
     }
 
+
+    public static boolean canThreePartsEqualSum2(int[] arr) {
+        int sum = 0;
+        for (int a : arr) {
+            sum += a;
+        }
+        if (sum % 3 != 0) return false;
+        int target = sum / 3;
+        sum = 0;
+        int i = 0;
+        while (i < arr.length) {
+            sum += arr[i];
+            if (sum == target) {
+                break;
+            }
+            i++;
+        }
+        if (sum != target) return false;
+        int j = i + 1;
+        while (j < arr.length - 1) {
+            sum += arr[j];
+            if (sum == 2 * target) {
+                return true;
+            }
+            j++;
+        }
+        return false;
+    }
+
+
     public static void main(String[] args) {
-        int[] a = new int[]{3, 3, 6, 5, -2, 2, 5, 1, -9, 4};
+        int[] a = new int[]{1, -1, 1, -1};
         System.out.println(canThreePartsEqualSum(a));
     }
 }