Backward Digit Sums (POJ-3187)

Would have thought it would time out, it seems to think more, 63ms, it seems that the ability to judge the complexity of time or not AH. This question is exactly where the next_permutation () function comes in.

#include <cstdio> #include <cstring> #include <iostream> #include <algorithm> #include < Queue> #include <cmath>using namespace Std;int n,sum,a[100],a[100];int main () {    scanf ("%d%d", &n, &sum);    for (int i=0;i<n;i++) a[i] = i+1;    Do {for        (int i=0;i<n;i++) a[i] = A[i];        int cur = n;        bool OK = false;        if (n==1) {printf ("1\n"); return 0;}        while (true) {for            (int i=0;i<cur-1;i++) a[i] = a[i]+a[i+1];            if (cur==2) {                if (a[0]==sum) ok = true;                break;            }            cur--;        }        if (OK) {            printf ("%d", a[0]);            for (int i=1;i<n;i++) printf ("%d", A[i]);            printf ("\ n");            break;        }    } while (Next_permutation (a,a+n));    return 0;}

Backward Digit Sums (POJ-3187)