POJ 2891 Strange Way to Express Integers --- 中国剩余定理扩展模板题

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本文链接： https://blog.csdn.net/lmhlmh_/article/details/100167480

题解 https://blog.csdn.net/litble/article/details/75807726

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
const int maxn = 1e5+20;
int n;
ll m[maxn],a[maxn];

ll ex_gcd(ll a,ll b,ll &x,ll &y) {
    if(b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    ll t = ex_gcd(b,a%b,y,x);
    y -= a/b*x;
    return t;
}

ll solve() {
    ll pre_a = a[1],pre_m = m[1];
    for(int i = 2;i <= n;i++) {
        ll x1,x2;
        ll d = ex_gcd(pre_m,m[i],x1,x2);
        if((a[i]-pre_a)%d!=0) return -1;
        x1 *= (a[i]-pre_a)/d;
        ll t = m[i] / d;
        x1 = (x1%t+t)%t;
        pre_a = pre_a+x1*pre_m;
        pre_m = pre_m/d*m[i];
        pre_a = pre_a%pre_m;
    }
    pre_a = (pre_a%pre_m+pre_m)%pre_m;
    return pre_a;
}

int main() {
    int i;
    while(scanf("%d",&n) != EOF) {
        for(int i = 1;i <= n;i++) {
            scanf("%lld%lld",&m[i],&a[i]);
        }
        printf("%lld\n",solve());
    }

    return 0;
}