class Solution724 {
public int pivotIndex(int[] nums) {
int sum=0;
for(int num:nums){
sum+=num;
}
int leftSum=0;
int rightSum=0;
for(int i=0;i<nums.length;i++){
if(i==0){
leftSum=0;
}else{
leftSum+=nums[i-1];
}
rightSum=sum-nums[i]-leftSum;
if(rightSum==leftSum){
return i;
}
}
return -1;
}
}