验证四方定理

#include<cstdio>int mode_1(int n){    int i;    for(i=1;i<n;i++)        if(i*i==n)        {            printf("%d*%d=%d\n",i,i,n);            return 1;        }    return 0;}int mode_2(int n){    int i,j;    for(i=1;i*i<n;i++)        for(j=i;j*j<n;j++)            if(i*i+j*j==n)            {                printf("%d^2+%d^2=%d\n",i,j,n);                return 1;            }    return 0;}int mode_3(int n){    int i,j,k;    for(i=1;i*i<n;i++)        for(j=i;j*j<n;j++)            for(k=j;k*k<n;k++)            if(i*i+j*j+k*k==n)            {                printf("%d^2+%d^2+%d^2=%d\n",i,j,k,n);                return 1;            }    return 0;}int mode_4(int n){    int i,j,k,l;    for(i=1;i*i<n;i++)        for(j=i;j*j<n;j++)            for(k=j;k*k<n;k++)                for(l=k;l*l<n;l++)            if(i*i+j*j+k*k+l*l==n)            {                printf("%d^2+%d^2+%d^2+%d^2=%d\n",i,j,k,l,n);                return 1;            }    return 0;}void prove(int n){    if(mode_1(n))        printf("It has vertified Four Square theorem\n");    else if(mode_2(n))        printf("It has vertified Four Square theorem\n");    else if(mode_3(n))        printf("It has vertified Four Square theorem\n");    else if(mode_4(n))        printf("It has vertified Four Square theorem\n");    else        printf("ERROR!");}int main(){    int n;    scanf("%d",&n);    prove(n);    return 0;}