[LeetCode]Jump Game

class Solution {
//O(n^2) TLE
//using segment overlap O(nlogn)
public:
struct Seg
{
int x, y;
Seg(int _x=0, int _y=0):x(_x),y(_y){}
bool operator < (const Seg& rhs) const
{
if(x != rhs.x) return x < rhs.x;
else return y < rhs.y;
}
};
bool canJump(int A[], int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(0 == n) return false;
vector<Seg> seg(n);
for (int i = 0; i < n; ++i)
seg[i] = Seg(i, i+A[i]);
sort(seg.begin(), seg.end());
//then process
int reach = 0;
for (int i = 0; i < n; ++i)
if(seg[i].x <= reach) reach = max(reach, seg[i].y);
if(reach >= n-1) return true;
else return false;
}
};

class Solution {
public:
bool canJump(int A[], int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int start = 0;
int end = 0;
while(end < n-1)
{
int newEnd = start;
for(int i = start; i <= end; ++i) newEnd = max(newEnd, i+A[i]);
if(newEnd == end) return false;
start = end+1;
end = newEnd;
}
if(end >= n-1) return true;
else return false;
}
};