#include <stdio.h>
int findElementThatAppearsOnceInArray(int vec[], int size) {
int map[1024] = {0};
for (int i = 0; i < size; ++i) {
map[vec[i]]++;
}
for (int i = 0; i < 1000; ++i) {
if (map[i] == 1) {
return i;
}
}
return -1;
}
int main() {
int vec[] = {3, 5, 5, 2, 7, 3, 2, 8, 8, 3, 2, 5, 8};
int size = sizeof(vec) / sizeof(vec[0]);
printf("%d\n", findElementThatAppearsOnceInArray(vec, size));
return 0;
}
/*
run:
7
*/