[Leetcode] Jump Game / Jump Game II

Jump Game Mar 25 '12 6923 / 16241

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Determine if you are able to reach the last index.

For example:
A = [2,3,1,1,4], return true.

A = [3,2,1,0,4], return false.

 

Jump Game II Mar 17 '12 6747 / 18561

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Your goal is to reach the last index in the minimum number of jumps.

For example:
Given array A = [2,3,1,1,4]

The minimum number of jumps to reach the last index is 2. (Jump 1 step from index 0 to 1, then 3 steps to the last index.)

 

class Solution {
public:
    bool canJump(int A[], int n) {
        int last = 0, t;
        for (int i = 0; i < n; i++) {
            if (i <= last) {
                t = i + A[i];
                if (last < t) last = t;
                if (last >= n-1) return true;
            } else return false;
        }
        return last >= n-1;
    }
};


class Solution {
public:
    int jump(int A[], int n) {
        int last = 0, step = 0, cur = 0, t;
        while (last < n-1) {
            int nextlast = last;
            for (int i = cur; i <= last; i++) {
                t = i + A[i];
                if (t > nextlast) nextlast = t;
            }
            step++;
            cur = last + 1;
            last = nextlast;
        }
        return step;
    }
};