用栈来解决这类问题, 很简单
/**
* @param {string} S
* @return {string}
*/
const removeDuplicates = function (S) {
let stackString = '';
for (let i = 0; i < S.length; i++) {
const element = S[i];
if (stackString.length === 0) {
stackString += element;
} else if (stackString.length !== 0 && stackString[stackString.length - 1] === element) {
while (stackString[stackString.length - 1] === element) {
stackString = stackString.slice(0, stackString.length - 1);
}
} else {
stackString += element;
}
}
return stackString;
};