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// 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
}
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