LeetCode 75
Find Pivot Index
- Problem
- LC 724
- Topic
- Prefix Sum
- File
- official75_LC724FindPivotIndex.java
- Path
- pkg5leetcode/official75/official75_LC724FindPivotIndex.java
- Package
- pkg5leetcode.official75
- Command
- java pkg5leetcode/official75/official75_LC724FindPivotIndex.java
- Approach
- Prefix sum; pivot where left sum equals right sum.
- Complexity
- Time O(n), Space O(1)
There is no in-browser runner. This is the file from the curriculum, unchanged.
1package pkg5leetcode.official75;2 3/*4 * Find Pivot Index | LC 7245 * APPROACH: Prefix sum; pivot where left sum equals right sum.6 * COMPLEXITY: Time O(n), Space O(1)7 */8public class official75_LC724FindPivotIndex {9 static int pivotIndex(int[] nums) {10 int total = 0;11 for (int n : nums) total += n;12 int left = 0;13 for (int i = 0; i < nums.length; i++) {14 if (left == total - left - nums[i]) return i;15 left += nums[i];16 }17 return -1;18 }19 20 public static void main(String[] args) {21 check(pivotIndex(new int[]{1,7,3,6,5,6}) == 3, "case1");22 check(pivotIndex(new int[]{1,2,3}) == -1, "case2");23 check(pivotIndex(new int[]{2,1,-1}) == 0, "case3");24 System.out.println("all tests passed");25 }26 27 static void check(boolean cond, String name) {28 if (!cond) throw new AssertionError("FAILED: " + name);29 System.out.println(" PASS " + name);30 }31}