JavaScript Simple Solution (Faster than 99.4%)
javascript\nconst modifyString = function(s) {\n  let res = [...s];\n  \n  for (let i = 0; i < res.length; i++) {\n    if (res[i] !== "?") continue;\n    if (re
```javascript\nconst modifyString = function(s) {\n  let res = [...s];\n  \n  for (let i = 0; i < res.length; i++) {\n    if (res[i] !== "?") continue;\n    if (res[i-1] !== "a" && res[i+1] !== "a") { res[i] = "a"; continue; }\n    if (res[i-1] !== "b" && res[i+1] !== "b") { res[i] = "b"; continue; }\n    res[i] = "c";\n  }\n  \n  return res.join("");\n};\n```
['JavaScript']