leetcode

commit a3e480ab5b7b3d246910c8a21477910ea6c6f691
parent b4d2c1ef78bb9e9455e01153d2f80c0fa5e7d64c
Author: Jack Sangdahl <jack@pngu.org>
Date:   Sat,  6 Jun 2026 09:58:00 -0600

2574. left and right sum differences

Diffstat:
A
left_right_sum_diff.c
 | 
45
+++++++++++++++++++++++++++++++++++++++++++++
A
left_right_sum_diff.py
 | 
30
++++++++++++++++++++++++++++++

2 files changed, 75 insertions(+), 0 deletions(-)
diff --git a/left_right_sum_diff.c b/left_right_sum_diff.c
@@ -0,0 +1,45 @@
+// 2574. Left and Right Sum Differences
+#include "leetcode.h"
+
+/*
+ * you are given a 0-indexed integer array 'nums' of size 'n'. define two arrays
+ * 'leftSum' and 'rightSum' where 'leftSum[i]' is the sum of elements to the
+ * left of index 'i' in the array 'nums'. if there is no such element,
+ * 'leftSum[i] = 0'. and vice-versa for 'rightSum'. return an integer array
+ * 'answer' of size 'n' where 'answer[i] = |leftSum[i] - rightSum[i]|'.
+ */
+
+int *leftRightDifference(int *nums, int numsSize, int *returnSize) {
+  *returnSize = numsSize;
+  int *left_sum = (int *)calloc(numsSize, sizeof(int));
+  int *right_sum = (int *)calloc(numsSize, sizeof(int));
+  int *ans = (int *)malloc(numsSize * sizeof(int));
+  for (int i = 1; i < numsSize; i++)
+    left_sum[i] = left_sum[i - 1] + nums[i - 1];
+  for (int j = numsSize - 2; j >= 0; j--)
+    right_sum[j] = right_sum[j + 1] + nums[j + 1];
+  for (int k = 0; k < numsSize; k++)
+    ans[k] = abs(left_sum[k] - right_sum[k]);
+  free(left_sum);
+  free(right_sum);
+  return ans;
+}
+
+int main() {
+  int n1[] = {10, 4, 8, 3}, rs1, r1[] = {15, 1, 11, 22};
+  int n2[] = {1}, rs2, r2[] = {0};
+  int *lrd1 = leftRightDifference(n1, ARRAY_SIZE(n1), &rs1);
+  int *lrd2 = leftRightDifference(n2, ARRAY_SIZE(n2), &rs2);
+  for (int i = 0; i < rs1; i++) {
+    printf("%d ", lrd1[i]);
+    assert(lrd1[i] == r1[i]);
+  }
+  printf("\n");
+  for (int i = 0; i < rs2; i++) {
+    printf("%d ", lrd2[i]);
+    assert(lrd2[i] == r2[i]);
+  }
+  printf("\n");
+  free(lrd1);
+  free(lrd2);
+}
diff --git a/left_right_sum_diff.py b/left_right_sum_diff.py
@@ -0,0 +1,30 @@
+# 2574. Left and Right Sum Differences
+
+"""
+you are given a 0-indexed integer array 'nums' of size 'n'. define two arrays
+'leftSum' and 'rightSum' where 'leftSum[i]' is the sum of elements to the
+left of index 'i' in the array 'nums'. if there is no such element,
+'leftSum[i] = 0'. and vice-versa for 'rightSum'. return an integer array
+'answer' of size 'n' where 'answer[i] = |leftSum[i] - rightSum[i]|'.
+"""
+
+
+class Solution:
+    def leftRightDifference(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        left_sum = [0] * n
+        right_sum = [0] * n
+        ans = [0] * n
+        for i in range(1, n):
+            left_sum[i] = left_sum[i - 1] + nums[i - 1]
+        for j in range(n - 2, -1, -1):
+            right_sum[j] = right_sum[j + 1] + nums[j + 1]
+        for k in range(n):
+            ans[k] = abs(left_sum[k] - right_sum[k])
+        return ans
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    print(obj.leftRightDifference(nums=[10, 4, 8, 3]))
+    print(obj.leftRightDifference(nums=[1]))