1300-sum-of-mutated-array-closest-to-target.js

/**
 * @param {number[]} arr
 * @param {number} target
 * @return {number}
 */
const findBestValue = function(arr, target) {
  let l, r, mi, s = 0, m = -1;
  for(let v of arr) { s += v; m = Math.max(m, v); }
  if(s <= target) return m; 

  for(l = 1, r = m; l < r;) {
    mi = ~~((l+r)/2);
    s = 0;
    for(let v of arr) s += (v > mi) ? mi : v;
    if(s >= target) r = mi;
    else          l = mi + 1;
  }
  // check if we are 1 step off the target 
  let s1=0,s2=0;
  for(let v of arr) {
    s1 += (v>l)?(l):v;
    s2 += (v>l-1)?(l-1):v;
  }

  return (Math.abs(s2-target) <= Math.abs(s1-target)) ? l-1 : l;
};