README_EN.md

1871. Jump Game VII

中文文档

Description

You are given a 0-indexed binary string s and two integers minJump and maxJump. In the beginning, you are standing at index 0, which is equal to '0'. You can move from index i to index j if the following conditions are fulfilled:

• i + minJump <= j <= min(i + maxJump, s.length - 1), and
• s[j] == '0'.

Return true if you can reach index s.length - 1 in s, or false otherwise.

 

Example 1:

Input: s = "011010", minJump = 2, maxJump = 3
Output: true
Explanation:
In the first step, move from index 0 to index 3. 
In the second step, move from index 3 to index 5.

Example 2:

Input: s = "01101110", minJump = 2, maxJump = 3
Output: false

 

Constraints:

• 2 <= s.length <= 105
• s[i] is either '0' or '1'.
• s[0] == '0'
• 1 <= minJump <= maxJump < s.length

Solutions

Python3

class Solution:
    def canReach(self, s: str, minJump: int, maxJump: int) -> bool:
        n = len(s)
        dp = [False] * n
        dp[0] = True
        pre_sum = [0] * (n + 1)
        pre_sum[1] = 1
        for i in range(1, n):
            if s[i] == '0':
                l = max(0, i - maxJump)
                r = i - minJump
                if r >= l and pre_sum[r + 1] - pre_sum[l] > 0:
                    dp[i] = True
            pre_sum[i + 1] = pre_sum[i] + dp[i]
        return dp[n - 1]

Java

class Solution {
    public boolean canReach(String s, int minJump, int maxJump) {
        int n = s.length();
        boolean[] dp = new boolean[n];
        dp[0] = true;
        int[] preSum = new int[n + 1];
        preSum[1] = 1;
        for (int i = 1; i < n; ++i) {
            if (s.charAt(i) == '0') {
                int l = Math.max(0, i - maxJump);
                int r = i - minJump;
                if (r >= l && preSum[r + 1] - preSum[l] > 0) {
                    dp[i] = true;
                }
            }
            preSum[i + 1] = preSum[i] + (dp[i] ? 1 : 0);
        }
        return dp[n - 1];
    }
}

JavaScript

/**
 * @param {string} s
 * @param {number} minJump
 * @param {number} maxJump
 * @return {boolean}
 */
var canReach = function (s, minJump, maxJump) {
    let n = s.length;
    let dp = new Array(n).fill(0);
    let sum = new Array(n + 1).fill(0);
    dp[0] = 1;
    sum[1] = 1;
    for (let i = 1; i < n; i++) {
        if (s.charAt(i) == '0') {
            let left = Math.max(0, i - maxJump);
            let right = i - minJump;
            if (left <= right && sum[right + 1] - sum[left] > 0) {
                dp[i] = 1;
            }
        }
        sum[i + 1] = sum[i] + dp[i];
    }
    return dp.pop();
};

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