Reverse Binary Strings

Reverse Binary Strings

Ideas

This kind of problem focuses on the result, not the alternating process

If it hits $00$ , then find the next$11$ , the middle$01$ all reverse.

So a $00$ , you need to consume a$11$ to restore$01/10$

So record $00,$ the number of$1$$1$$c1,c2$

Just take the maximum value between the two.

If $c1!=c2$ , there may be001 001 at theend$001$ is not consumed in pairs at this time.

#include <bits/stdc++.h>
using namespace std;
const int maxn=2e5+10;
int n;
char s[maxn];
 
void work() {
    
    
    scanf("%d", &n);
    scanf("%s", s);
    int ans1 = 0, ans0 = 0;
    for (int i = 0; i < n - 1; i++) {
    
    
        if (s[i] == '1' && s[i + 1] == '1') ans1++;
        if (s[i] == '0' && s[i + 1] == '0') ans0++;
    }
    printf("%d\n", max(ans1, ans0));
}
 
int main() {
    
    
    int _;
    scanf("%d", &_);
    while (_--) {
    
    
        work();
    }
    return 0;
}