题目 https://cn.vjudge.net/problem/URAL-1133
题意 给你斐波那契数的某两项，求第n项
思路 暴力二分给的下标小的的第二项 用另一个验证
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll a[10000];
ll x1,x2,x3,y1,y2;
int ok(ll x)
{a[x1] = y1;a[x1+1] = x;for(ll i=x1+2;i<=x2;i++){a[i] = a[i-1] + a[i-2];if(a[i] > 2e9) return 1;else if(a[i] < -2e9) return -1;}if(y2 < a[x2]) return 1;else if(y2 > a[x2]) return -1;return 0;
}
ll solve(ll x)
{a[x1] = y1,a[x1+1] = x;if(x3 > x1){for(ll i=x1+2;i<=x3;i++){a[i] = a[i-1] + a[i-2];}return a[x3];}else{for(ll i=x1-1;i>=x3;i--){a[i] = a[i+2] - a[i+1];}return a[x3];}
}int main()
{ll n,m,i,j;scanf("%lld%lld%lld%lld%lld",&x1,&y1,&x2,&y2,&x3);x1 += 3000,x2 += 3000,x3 += 3000;if(x1 > x2){swap(x1,x2);swap(y1,y2);}ll l = -2e9,r = 2e9;while(r > l + 1){ll mid = (l+r)/2;if(ok(mid) > 0){r = mid;}else if(ok(mid) < 0){cout<<mid<<endl;l = mid;}else{ll ans = solve(mid);printf("%lld\n",ans);break;}}return 0;
}