[Leetcode] [JavaScript] Self Crossing

Self Crossing

You is given an array x of n positive numbers. You start at point (0,0) and moves x[0] metres to the north, then x[1] metres to the west, x[2] metres to the South, metres to the east and so on. In the other words, after each move your direction changes counter-clockwise.

Write a one-pass algorithm O(1) with extra space to determine, if your path crosses itself, or not.

Example 1:

x [2, 1, 1, 2] , Return true (self crossing)

Example 2:

x [1, 2, 3, 4] , Return false (not self crossing)

Example 3:

x [1, 1, 1, 1] , Return true (self crossing)

https://leetcode.com/problems/self-crossing/

Draw the line counterclockwise to find out if the line has a cross.

See figure, three cases, corresponding to the comments in the code.

 

1 /**2 * @param {number[]} x3 * @return {Boolean}4  */5 varIsselfcrossing =function(x) {6      for(vari = 3; i < x.length; i++){7         //I. [2, 1, 1, 2]8         if(X[i-3] && x[i] >= x[i-2] && x[i-1] <= x[i-3]) 9             return true;Ten         //Ii. [1, 1, 2, 1, 1] One         if(X[i-4] && x[i-3] = = = X[i-1] && x[i-4] + x[i] >= x[i-2])  A             return true; -         //Iii. [1, 1, 2, 2, 1, 1] -         if(X[i-5] && x[i-4] <= x[i-2] && x[i] + x[i-4] >= x[i-2]  the&& x[i-3] >= x[i-1] && x[i-5] + x[i-1] >= x[i-3])  -             return true; -     } -     return false; +};

[Leetcode] [JavaScript] Self Crossing