二分|回溯

 

 

 

 

 

08.12 八皇后

    bool col[1000] = {false};  // init
bool diga[1000] = {false};
bool digb[2000] = {false};  

class Solution {
vector<vector<string>> ret;
vector<string> path;
bool col[1000] = {false};  // init
bool diga[1000] = {false};
bool digb[2000] = {false};  
int n;
public:
vector<vector<string>> solveNQueens(int n) {
this->n = n;
path.resize(n, string(n, '.'));
dfs(0);
return ret;
}

void dfs(int r) {
if (r == n) {
ret.push_back(path);
return;
}

for (int i = 0; i < n; i++) {
if (!col[i] && !diga[i + r] && !digb[i - r + 1000]) {  
path[r][i] = 'Q';
col[i] = diga[i + r] = digb[i - r + 1000] = true;  
dfs(r + 1);
col[i] = diga[i + r] = digb[i - r + 1000] = false;  
path[r][i] = '.';
}
}
}
};

 

 

lc410

二分

class Solution {
public:
int splitArray(vector<int>& nums, int k) 
{
int n=nums.size();
int mx=0,sum=0;
for(auto& num:nums)
{
sum+=num;
mx=max(mx,num);
}

int l=mx;
int r=sum;

function<bool(int)> can=[&](int mid)
{
int cnt=0,sum=0;
for(auto& num:nums)
{
sum+=num;
if(sum>mid)
{
cnt++;
sum=num;
}
}
if(cnt<k)
return true;
else
return false;
};

while(l<=r)
{
int mid=l+(r-l)/2;

if(can(mid))
{
r=mid-1;
}
else
{
l=mid+1;
}
}
return l;
}

};