Leetcode55Jump Game

題目

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.

思路

找每一次走的最大值

測試用例

[1,1,1,1,1,1,1,1,1,1,1,1....,1,1,1]
[0]
[1,2,3,4]

代碼

package leetcodeArray;

/**
 * 
    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.
 * @author wq
 *
 */
public class Leetcode55JumpGame {
    public boolean canJump(int[] nums) {
        int i = 0; 
        for(int reach = 0; i < nums.length && i <= reach; ++i){
            reach = Math.max(nums[i] + i , reach);
        }

        return i == nums.length;
    }
}

他山之玉

bool canJump(int A[], int n) {
    int i = 0;
    for (int reach = 0; i < n && i <= reach; ++i)
        reach = max(i + A[i], reach);
    return i == n;
}

bool canJump(int A[], int n) {
    int last=n-1,i,j;
    for(i=n-2;i>=0;i--){
        if(i+A[i]>=last)last=i;
    }
    return last<=0;
}