Jump Game

Source

You are given an integer array nums.
You are initially positioned at the array's first index, and each element in the array represents your maximum jump length at that position.

Return true if you can reach the last index, or false otherwise.

Constraints

• 1 <= nums.length <= 104
• 0 <= nums[i] <= 105

Concept

The idea is to iterate entire loop and set variable reach by max(reach, i+nums[i]), when the indexer i exceed reach which means we couldn't jump to the end with current value.

Code

class Solution {
public:
    bool canJump(vector<int>& nums) {
        /** 2022/1/6 -- O(N), O(1); Greedy */
        int n = nums.size();
        if (n == 1) return true;

        int i = 0;
        for (int reach=0; i<n && i<=reach; i++) { // We add `i<=reach` to let i escape from loop earlier
            reach = max(reach, i+nums[i]);
        }

        return i == n;
    }
};