-
Notifications
You must be signed in to change notification settings - Fork 0
/
13 March.cpp
60 lines (50 loc) · 1.17 KB
/
13 March.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
// class Solution {
// public:
// int pivotInteger(int n) {
// int sum = 0;
// for(int i = 1 ; i <= n ; i++){
// sum += i;
// }
// for(int i = 1; i <= n ; i++){
// int ans = 0;
// ans += i;
// if(ans == sum - ans + i)return i;
// }
// return -1;
// }
// };
class Solution {
public:
int pivotInteger(int n) {
int totalSum = n * (n + 1) / 2; // Sum of all elements from 1 to n
int prefixSum = 0;
for (int i = 1; i <= n; i++) {
prefixSum += i;
if (prefixSum == totalSum - prefixSum + i) {
return i;
}
}
return -1;
}
};
// Binary search solution
class Solution {
public:
int pivotInteger(int n) {
int left = 1;
int right = n;
while (left <= right) {
int x = (left + right) / 2;
int leftSum = (x * (x + 1)) / 2;
int rightSum = ((n * (n + 1)) / 2) - leftSum; w
if (leftSum == rightSum) {
return x;
} else if (leftSum < rightSum) {
left = x + 1;
} else {
right = x - 1;
}
}
return -1;
}
};