Approach: Sliding window with at most k zeros

def longestOnes(nums, target):
    l = zeros = best = 0
    for r in range(len(nums)):
        if nums[r] == 0: zeros += 1
        while zeros > target:
            if nums[l] == 0: zeros -= 1
            l += 1
        best = max(best, r - l + 1)
    return best

Complexity: O(n) time, O(1) space.

Full Solution — all languages

class Solution:
    def longestOnes(self, nums, target):
        l = zeros = best = 0
        for r in range(len(nums)):
            if nums[r] == 0:
                zeros += 1
            while zeros > target:
                if nums[l] == 0:
                    zeros -= 1
                l += 1
            best = max(best, r - l + 1)
        return best

import java.util.*;
class Solution {
    public int longestOnes(int[] nums, int target) {
        int l = 0, zeros = 0, best = 0;
        for (int r = 0; r < nums.length; r++) {
            if (nums[r] == 0) zeros++;
            while (zeros > target) {
                if (nums[l] == 0) zeros--;
                l++;
            }
            best = Math.max(best, r - l + 1);
        }
        return best;
    }
}

#include <bits/stdc++.h> using namespace std;
class Solution {
    public: int longestOnes(vector<int>& nums, int target) {
        int l = 0, zeros = 0, best = 0;
        for (int r = 0; r < (int)nums.size(); r++) {
            if (nums[r] == 0) zeros++;
            while (zeros > target) {
                if (nums[l] == 0) zeros--;
                l++;
            }
            best = max(best, r - l + 1);
        }
        return best;
    }
};

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */ var longestOnes = function(nums, target) {
    let l = 0, zeros = 0, best = 0;
    for (let r = 0; r < nums.length; r++) {
        if (nums[r] === 0) zeros++;
        while (zeros > target) {
            if (nums[l] === 0) zeros--;
            l++;
        }
        best = Math.max(best, r - l + 1);
    }
    return best;
};

Max Consecutive Ones III

Example 1

Example 2

Constraints