Algorithm
Problem Name: 55. Jump Game
Problem Link: https://leetcode.com/problems/jump-game/
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.
Example 1:
Input: nums = [2,3,1,1,4] Output: true Explanation: Jump 1 step from index 0 to 1, then 3 steps to the last index.
Example 2:
Input: nums = [3,2,1,0,4] Output: false Explanation: You will always arrive at index 3 no matter what. Its maximum jump length is 0, which makes it impossible to reach the last index.
Constraints:
1 <= nums.length <= 1040 <= nums[i] <= 105
Code Examples
#1 Code Example with C Programming
Code -
C Programming
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
bool canJump0(int* nums, int numsSize) {
if (nums == NULL || numsSize == 0) return false;
/* remain steps from 0 to i */
int *dp = (int *)calloc(numsSize, sizeof(int));
dp[0] = 0;
int i;
for (i = 1; i < numsSize; i++) {
if (dp[i - 1] > nums[i - 1]) {
dp[i] = dp[i - 1] - 1;
}
else {
dp[i] = nums[i - 1] - 1;
}
if (dp[i] < 0) return false;
}
bool can = (dp[numsSize - 1] >= 0);
free(dp);
return can;
}
bool canJump1(int* nums, int numsSize) {
if (nums == NULL || numsSize == 0) return false;
int remain_steps = 0;
int i;
for (i = 1; i < numsSize; i++) {
if (remain_steps < nums[i - 1]) {
remain_steps = nums[i - 1] - 1;
}
else {
remain_steps--;
}
if (remain_steps < 0) return false;
}
return (remain_steps >= 0);
}
bool canJump(int* nums, int numsSize) {
if (nums == NULL || numsSize == 0) return false;
int max_dist = 0; /* max distance we can get */
int i;
/* if we can get to i continue, otherwise exit loop and return false */
for (i = 0; i < numsSize && i <= max_dist; i++) {
if (nums[i] + i > max_dist) {
max_dist = nums[i] + i;
}
/* if we already reach the destination, exit loop and return true */
if (max_dist >= numsSize - 1) return true;
}
return false;
}
int main() {
int nums0[] = { 2, 3, 1, 1, 4 };
int nums1[] = { 3, 2, 1, 0, 4 };
int nums2[] = { 2, 5, 0, 0 };
int nums3[] = { 0 };
assert(canJump(nums0, sizeof(nums0) / sizeof(nums0[0])) == true);
assert(canJump(nums1, sizeof(nums1) / sizeof(nums1[0])) == false);
assert(canJump(nums2, sizeof(nums2) / sizeof(nums2[0])) == true);
assert(canJump(nums3, sizeof(nums3) / sizeof(nums3[0])) == true);
printf("all test passed!\n");
return 0;
}
Input
nums = [2,3,1,1,4]
Output
true
#2 Code Example with C++ Programming
Code -
C++ Programming
class Solution {
public:
bool canJump(vector<int>& nums) {
int distance = 0;
for(int i = 0; i < nums.size() - 1; i++){
distance = max(distance, i + nums[i]);
if(distance == i) return false;
}
return true;
}
};
Input
nums = [3,2,1,0,4
Output
false
#3 Code Example with Java Programming
Code -
Java Programming
class Solution {
public boolean canJump(int[] nums) {
int reachable = 0;
for (int i=0; i < nums.length; ++i) {
if (i > reachable) return false;
reachable = Math.max(reachable, i + nums[i]);
}
return true;
}
}
Input
nums = [2,3,1,1,4]
Output
true
#4 Code Example with Javascript Programming
Code -
Javascript Programming
const canJump = function(nums) {
let max = 0
for(let i = 0, len = nums.length; i < len; i++) {
if(i <= max && nums[i] > 0) {
max = Math.max(max, i + nums[i])
}
}
return max >= nums.length - 1
};
Input
nums = [2,3,1,1,4]
Output
true
#5 Code Example with Python Programming
Code -
Python Programming
class Solution:
def canJump(self, nums):
"""
:type nums: List[int]
:rtype: bool
"""
i = mx = 0
while i < len(nums) and i <= mx:
if nums[i] + i >= len(nums) - 1: return True
mx, i = max(mx, i + nums[i]), i + 1
return False
Input
nums = [3,2,1,0,4]
Output
false
#6 Code Example with C# Programming
Code -
C# Programming
namespace LeetCode
{
public class _055_JumpGame
{
public bool CanJump(int[] nums)
{
int maxRight = 0;
for (int i = 0; i < nums.Length; i++)
{
if (i > maxRight) { return false; }
if (i + nums[i] > maxRight)
maxRight = i + nums[i];
if (maxRight >= nums.Length - 1)
return true;
}
return false;
}
}
}
Input
nums = [3,2,1,0,4]
Output
false