// 2780. Minimum Index of a Valid Split #include "leetcode.h" /* * an element 'x' of an integer array 'arr' of length 'm' is dominant if more * than half the elements of 'arr' have a value of 'x'. you are given a * 0-indexed integer array 'nums' of length 'n' with one dominant element. you * can split 'nums' at an index 'i' into two arrays 'nums[0, ..., i]' and * 'nums[i + 1, ..., n - 1]', but the split is only valid if '0 <= i < - 1' and * the two arrays have the same dominant element. return the minimum index of a * valid split. if no split exists, return -1. */ int minimumIndex(int *nums, int numsSize) { int dominant = nums[0], cnt = 0; for (int i = 0; i < numsSize; i++) { cnt = nums[i] == dominant ? cnt + 1 : cnt - 1; if (!cnt) { dominant = nums[i]; cnt = 1; } } int left = 0; for (int i = 0; i < numsSize; i++) if (nums[i] == dominant) left++; cnt = 0; for (int i = 0; i < numsSize; i++) { if (nums[i] == dominant) cnt++; if (cnt * 2 > (i + 1) && (left - cnt) * 2 > (numsSize - i - 1)) return i; } return -1; } int main() { int n1[] = {1, 2, 2, 2}, n2[] = {2, 1, 3, 1, 1, 1, 7, 1, 2, 1}, n3[] = {3, 3, 3, 3, 7, 2, 2}; printf("%d\n", minimumIndex(n1, ARRAY_SIZE(n1))); // expect: 2 printf("%d\n", minimumIndex(n2, ARRAY_SIZE(n2))); // expect: 4 printf("%d\n", minimumIndex(n3, ARRAY_SIZE(n3))); // expect: -1 }