C ++ summarize some useful tips

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1. output two-dimensional array

You usually output two-dimensional array like this:

for(int i = 1; i <= n; ++i) {
    for(int j = 1; j <= m; ++j)
        printf("%d ", a[i][j]);
    printf("\n");
}

But you can so that the output:

for(int i = 1; i <= n; ++i)
　　for(int j = 1; j <= m; ++j)
　　　　printf("%d%c", a[i][j], " \n"[j == m]);

10 times is not only convenient, but also very forced grid.

The first two largest 2.O (n) in the required number of columns

Use the swap to do!

for(int i = 1; i <= n; ++i) {
　　int t = a[i];
　　if(t > big1) swap(big1, t);
　　if(t > big2) swap(big2, t);
}

Very convenient.

3.for Inflection

Here is the code for inflection. Nothing Senior C ++ syntax with 11.

// before the chain to star 
for ( int TU the p-= [U], v; v = to [the p-], the p-; the p-NXT = [the p-]) 

// tree ancestors back 
for (int p = u; p ; FA = P [P]) 

// find highbit 
for (ANS = 0; X; ANS ++, X = >>. 1); 

// A fast exponentiation 
for (ans = 1; x; a * = a, x >> = . 1) 
　　IF (. 1 & X) = A * ANS;

 

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