LeetCode Contest 241 Question 2: Minimum Number of Swaps to Make the Binary String Alternating

[lokeshchennamchetty]

What is the software you are using, for white board?

[keshavgupta]

public:
int minSwaps(string s) {
int ans = 0, n = s.length();
int count1 = count(s.begin(), s.end(), '1');
int count0 = count(s.begin(), s.end(), '0');
if(abs(count1-count0) > 1) return -1;
if(count1 > count0){
string start1 = "";
for(int i = 0; i<n; i++){
if(i&1) start1 = start1 + '0';
else start1 = start1 + '1';
}
for(int i = 0; i<n; i++){
if(start1[i] != s[i]) ans++;
}
}
else if(count0 > count1){
string start0 = "";
for(int i = 0; i<n; i++){
if(i&1) start0 =start0 + '1';
else start0 = start0 + '0';
}
for(int i = 0; i<n; i++){
if(start0[i] != s[i]) ans++;
}
}
else if(count0 == count1){
int c0 = 0, c1 = 0;
string start0 = "";
for(int i = 0; i<n; i++){
if(i&1) start0 = start0 + '1';
else start0 = start0 + '0';
}
string start1 = "";
for(int i = 0; i<n; i++){
if(i&1) start1 = start1 + '0';
else start1 = start1 + '1';
}
for(int i = 0; i<n; i++){
if(start1[i] != s[i]) c1++;
if(start0[i] != s[i]) c0++;
}
ans = min(c0, c1);
}
return ans/2;
}
};
My code is bit lengthy any suggestion to reduce it.

[technologicalvivek]

Explanation is not proper.I think you know how to solve that question but not able explaning it.