FrogJump.js

function solution(X, A) {
    // write your code in JavaScript (Node.js 0.12)
    var count = new Array(X);
    
    for ( var i=0; i < A.length; i++) {
        var info = {
            minute : i,
            count : 1
        };
        //creates an object for the minute, count
        if (!count[A[i]])
         //if there is no count element (count) that the input array element (A[i]) 
            count[A[i]] = info;
            // we create that particular count[A[i]] to { minute: i, count: 1 }
        else {
            count[A[i]].count ++;
            // it exists and then ends up increasing the count
            if (count[A[i]].minute > info.minute) {
                count[A[i]]. minute = info.minute;
             // if the new minute value is larger than the original, reset
            }
        }
    }
    var latestTime = 0;
    for ( var i=1; i < count.length; i++) {
        if (!count[i]) {
            return -1    
        } else {
            if (latestTime < count[i].minute ) {
                latestTime = count[i].minute;
            }
        }
    }
  // if A is empty, returns 0
  // if count[i] iteration has a gap return -1
  // if count
    return latestTime;
}