JAVA

longest subarray with equal 0 and 1

private static int longestSubarrayWithEqualNumberOfZeroAndOne(int[]arr){

        // AyushG Notes
        // replace 0 with -1 int the given array and the problem will be converted to
        // longestSubarraySum problem with given sum = 0

        int currSum=0;
        int sum=0;
        int maxLen=0;
        for(int i=0; i<arr.length; i++){
            if(arr[i]==0){
                arr[i]=-1;
            }
        }
        HashMap<Integer,Integer> map = new HashMap<>();
        for(int i =0; i<arr.length; i++){
            currSum=currSum+arr[i];

            if(currSum==sum){
                maxLen=i+1;
            }
            if(!map.containsKey(currSum)){
                map.put(currSum,i);
            }
            if(map.containsKey(currSum-sum)){
                maxLen = Math.max(maxLen, i-map.get(currSum-sum));
            }
        }
        return maxLen;
    }